RETELL AI MASTERY

What This AI Receptionist Does

Your Retell AI receptionist qualifies inbound calls and routes them to the right outcome. It's not a general chatbot—it's a specialized qualification and routing system.

Three outcomes:

• Warm Transfer: For qualified callers. Agent gathers info, transfers with context whisper.
• Booking Link: For qualified callers when you're unavailable. Sends Calendly link via SMS.
• Polite Exit: For unqualified callers. Suggests alternatives professionally.

Who This Works Best For

Ideal for: Service businesses, consultants, agencies, freelancers, coaches, lawyers, accountants, designers, developers. High-touch sales requiring discovery calls. Appointment-based businesses. Small teams (1-10 people). Inbound lead generation.

Setting Realistic Expectations

Excellent at: Answering 24/7, asking all qualification questions, capturing info accurately, routing based on criteria, handling basic FAQ, sending booking links automatically.

Struggles with: Highly emotional callers, extremely complex questions, thick accents, callers who refuse to answer questions, situations requiring judgment outside defined criteria.

Expected success rate: 85-90% of calls handled successfully with proper setup.

Single-Prompt Agent (Recommended)

One unified system prompt controls the entire conversation. The LLM uses reasoning to decide what to say next.

Pros: Most flexible, easiest to modify, handles unexpected questions naturally, feels more human.

Cons: Can be unpredictable if prompt isn't clear, might skip questions.

Best for: Consultative sales, professional services, varied caller questions.

Multi-Prompt Agent

Multiple prompts for different conversation stages. Separate "modes" like Greeting, Qualification, FAQ.

Pros: More structured, easier to isolate stages.

Cons: Complex to maintain, awkward transitions, overkill for simple workflows.

Best for: Complex sales processes with distinct phases.

Conversation Flow Agent

Visual flowchart with drag-and-drop nodes representing questions and decisions.

Pros: 100% predictable, easy to visualize, perfect for scripted experiences.

Cons: Rigid, feels robotic, can't handle unexpected questions.

Best for: IVR replacement, surveys, simple yes/no qualification, compliance-heavy industries.

Our Recommendation

This course uses Single-Prompt Agent because it handles 95% of use cases, is easiest to learn and iterate, feels most human, and adapts naturally.

The Standard Qualification Flow

Define Your 5 Qualification Questions

Q1: Name and Company - "Can I get your name and company name?"

Q2: One-Sentence Need - "In one sentence, what do you need help with?"

Q3: Timeline/Urgency - "What's your timeline? When do you need this done?"

Q4: Budget/Decision - "Do you have a budget range?" OR "Are you the decision-maker?"

Q5: Email - "What's the best email to send you information?"

Define Your Transfer Criteria

What is a System Prompt?

Your agent's instruction manual (500-1500 words) that tells the LLM: who you are, what to do, how to conduct conversation, what questions to ask, when to transfer vs. book, how to handle edge cases, and what NOT to do.

Complete System Prompt Template

Step-by-Step: Customize Your Prompt

1. Copy template into Google Doc or text editor
2. Replace [YOUR BUSINESS NAME] (4 places)
3. Replace [BRIEF SERVICES DESCRIPTION]
4. Replace [YOUR NAME] (5 places)
5. Replace the 5 questions with your customized ones
6. Replace [YOUR HOURS] and timezone
7. Replace [YOUR SERVICES], [YOUR MINIMUM] criteria
8. Replace [COMMON TOPIC] with your FAQ
9. Read through—does it sound like YOUR business?
10. Save as "System Prompt v1"

Best Practices

• Be explicit—spell out every step
• Use structure—headers, bullets, lists
• One instruction per line
• Test and iterate—v1 won't be perfect
• Keep under 2000 words
• Use examples for specific phrasing

Your Greeting Script

The first thing callers hear. Must include AI disclosure and be 1-2 sentences (8-12 seconds).

Your Transfer Whisper

What YOU hear when your phone rings for a transfer. Gives you caller context before accepting.

The {curly brackets} are variables Retell replaces with actual data from qualification.

What Goes in Your Knowledge Base

Reference information your agent can search during calls: services, pricing, policies, FAQ, hours, contact info.

Knowledge Base Template

Step-by-Step: Create Your Knowledge Base

1. Copy template into new document
2. Replace SERVICES section with your actual services
3. Replace SERVICE AREA with your coverage
4. Replace PRICING with your ranges (don't be too specific—general ranges only)
5. Write 5-10 FAQ based on what you're commonly asked
6. Add your POLICIES (deposits, revisions, cancellation)
7. Add your BUSINESS HOURS and timezone
8. Add CONTACT INFO (leave phone blank for now)
9. Save as "Knowledge Base v1"

KB Writing Best Practices

• Keep answers short and direct
• Use simple language, avoid jargon
• One topic per section
• Use consistent formatting
• Update regularly based on common questions from call logs

Documents You Should Have

Before moving to Module 2, verify you've created:

• ✅ System Prompt v1 (fully customized, no [BRACKETS] remaining)
• ✅ Greeting script (8-12 seconds, includes AI disclosure)
• ✅ Transfer whisper template (with {variables})
• ✅ Knowledge Base v1 (all 6 sections filled)
• ✅ 5 qualification questions written
• ✅ Transfer criteria defined (minimum budget, timeline, etc.)

Understanding Phone Numbers in Retell

Retell provides phone numbers through their Twilio integration. When you purchase a number through Retell's dashboard, you're getting a Twilio-powered number that's automatically configured to work with Retell's voice infrastructure.

What you get: A dedicated phone number (local or toll-free) that routes incoming calls to your Retell agent. The number is yours as long as you maintain your Retell subscription. You can port this number out later if needed.

Pricing: Retell phone numbers cost approximately $2/month plus usage fees (inbound calls are ~$0.01/minute). This is significantly cheaper than traditional business phone services which typically start at $20-30/month per line.

Number types available:

• Local numbers: Area-code specific numbers (e.g., 212 for NYC, 415 for SF). Best for businesses serving a specific geographic region. Customers recognize the local area code and trust it more.
• Toll-free numbers: 800, 888, 877, 866, 855, 844, 833 prefixes. Best for national businesses or when you want to appear more established. Slightly more expensive (~$3-5/month).

Step-by-Step: Create Your Retell Account

If you haven't already created a Retell account, do this first:

1. Go to https://www.retellai.com
2. Click "Get Started" or "Sign Up" in the top right
3. Enter your email and create a password (use a password manager—you'll be logging in frequently during setup)
4. Verify your email address by clicking the link sent to your inbox
5. Complete the onboarding questions: business name, industry, primary use case
6. You'll land on the Retell Dashboard—this is your command center

Dashboard orientation: The left sidebar contains all major sections: Agents, Phone Numbers, Knowledge Base, Call Logs, and Settings. You'll use all of these throughout this course.

Step-by-Step: Purchase a Phone Number

Now let's get your number:

1. Navigate to Phone Numbers: In the left sidebar, click "Phone Numbers". You'll see an empty list if this is your first number.
2. Click "Purchase Phone Number": Look for the button in the top right of the phone numbers section. It's usually a blue button with a plus icon.
3. Choose your country: Select your country from the dropdown. For US-based businesses, select "United States". Retell supports phone numbers in 60+ countries.
4. Choose number type: Select "Local" or "Toll-Free". For most businesses, start with a local number in your primary business area code.
5. Search by area code: Enter your desired area code (e.g., 212, 310, 617). The system will show available numbers with that prefix.
6. Filter for patterns (optional): You can search for specific digit patterns if you want a memorable number (e.g., numbers ending in 0000 or with repeating digits).
7. Select your number: Browse the available numbers and click on one you like. Consider: Is it easy to remember? Does it look professional? Does it match your branding?
8. Review and confirm: You'll see the monthly cost and usage rates. Review these, then click "Purchase".
9. Payment method: If this is your first purchase, you'll need to add a payment method. Enter your card details. Retell uses Stripe for secure payment processing.
10. Purchase complete: Your number is now active and appears in your phone numbers list. It's ready to receive calls immediately.

Understanding Number Status and Binding

After purchasing, your number exists but isn't yet connected to an agent. You'll see a status indicator:

• "Unbound": Number is purchased but not connected to an agent. Calls to this number will go to a default Retell message.
• "Bound to [Agent Name]": Number is connected to a specific agent. Calls are routed to that agent.

Important: We'll bind the number to your agent in Module 3 after we create the agent. For now, just having the number purchased is sufficient.

Testing Your New Number (Basic Test)

Even though we haven't set up the full agent yet, you can test that the number works:

1. From your personal phone, dial the number you just purchased
2. You should hear a Retell default message like: "Thank you for calling. This number is not yet configured."
3. Hang up

If you hear this message, your number is working correctly. If you get a "number not in service" message, wait 2-3 minutes for provisioning to complete, then try again.

Why Business Hours Matter

Business hours control when your agent attempts warm transfers versus automatically sending booking links. This prevents the agent from trying to transfer calls to you at midnight or on weekends when you're unavailable.

How it works: When a call comes in during business hours, the agent can attempt transfer (if caller is qualified) or send booking link. When a call comes in outside business hours, the agent automatically skips transfer attempts and goes straight to booking or voicemail.

Voicemail as backup: Voicemail serves as a safety net. If someone calls and doesn't want to book via Calendly, or if there's a technical issue with the agent, they can leave a traditional voicemail that you'll receive as an audio file via email.

Step-by-Step: Set Business Hours

Configure when you're available for transfers:

1. Go to Phone Number Settings: In your Phone Numbers section, click on the number you just purchased. This opens the number's detail view.
2. Find "Business Hours" section: Scroll down to find the Business Hours configuration panel. It may also be under an "Advanced Settings" or "Routing" tab depending on your Retell dashboard version.
3. Set your timezone: Select your timezone from the dropdown. This is critical—if you're EST but select PST, your hours will be off by 3 hours. Common options: America/New_York (EST), America/Chicago (CST), America/Denver (MST), America/Los_Angeles (PST).
4. Configure weekly schedule: You'll see a grid with days of the week. For each day, you can:
   • Toggle the day on/off (some businesses are closed certain days)
   • Set start time (when you become available)
   • Set end time (when you stop taking transfers)
5. Example configuration: Monday through Friday, 9:00 AM to 5:00 PM. Saturday and Sunday, toggle to "Closed".
6. Set buffer times (optional): Some Retell plans allow you to set buffer times—periods at the start or end of your day when you accept bookings but not transfers. This gives you focus time.
7. Save your settings: Click the "Save" or "Update" button at the bottom of the section.

Step-by-Step: Record Your Voicemail Greeting

Set up a professional voicemail as a fallback:

1. Find Voicemail Settings: In the same phone number settings page, look for "Voicemail" or "After Hours Greeting" section.
2. Write your voicemail script: Keep it brief and include your booking link. Example script:
   "You've reached [Business Name]. We're currently unavailable, but we'd love to connect with you. For the fastest response, book a time at [YourBookingLink.com]. Or leave your name, number, and what you need help with, and we'll call you back within one business day. Thanks!"
3. Recording options: Retell offers two ways to record:
   • Record via phone: Click "Record by Phone", Retell calls you, you record the message, press # when done
   • Upload audio file: Record using your computer's voice memo app, save as MP3 or WAV, upload to Retell
4. Best practices for recording: Use a quiet room, speak clearly, smile while recording (it makes your voice sound warmer), speak at a moderate pace, record 2-3 takes and pick the best.
5. Test your voicemail: After saving, Retell should let you preview the recording. Listen to ensure it sounds clear and professional.
6. Enable voicemail: Toggle the "Enable Voicemail" switch to ON and save.

Understanding Voicemail Delivery

When someone leaves a voicemail, here's what happens:

• Recording captured: Retell records the message after your greeting plays
• Email notification: You receive an email with the voicemail as an audio attachment (usually MP3 or WAV format)
• Dashboard access: The voicemail also appears in your Retell dashboard under "Call Logs" with a voicemail tag
• Transcription (optional): Some Retell plans include automatic transcription of voicemails, so you can read them instead of listening

Set up a folder in your email specifically for Retell voicemails so they don't get lost in your inbox.

Why Calendly + Retell is Powerful

Calendly handles scheduling while Retell handles conversation. This separation of concerns is elegant and powerful:

• Automatic calendar sync: Calendly checks your Google/Outlook calendar and only shows available slots
• No double-bookings: When someone books, that slot immediately becomes unavailable
• Confirmations and reminders: Calendly automatically sends confirmation emails and reminder emails/SMS to reduce no-shows
• Prefilled data: Retell can pass caller information (name, email, company, need) directly into the booking form, so callers don't have to re-enter it

This creates a seamless experience: caller talks to AI, qualifies, receives booking link via SMS, clicks link, sees their info already filled in, picks a time, done.

Step-by-Step: Create Calendly Account (If Needed)

If you don't have Calendly yet:

1. Go to https://calendly.com
2. Click "Sign Up"
3. Sign up with Google (easiest—auto-connects your calendar) or email
4. Connect your calendar: Google Calendar, Outlook, or iCloud. This lets Calendly see when you're busy.
5. Set your availability: Choose which hours you're available for bookings. You can set different hours for different meeting types.
6. Complete the onboarding: Set your timezone, meeting location preferences (video call, phone, in-person), and notification preferences.

Calendly plan recommendation: The free plan works fine for this use case. It allows one event type and basic customization. Paid plans ($10-15/month) give you multiple event types, custom branding, and advanced features.

Step-by-Step: Create Your Booking Event

Now create the specific meeting type your AI will book:

1. Click "Create" or "+ New Event Type": From your Calendly dashboard, create a new event.
2. Choose event type: Select "One-on-One" (for 1:1 calls between you and the caller).
3. Name your event: Use a clear name like "Discovery Call", "Intro Call", "Consultation", or "Initial Meeting". This is what appears on the booking page.
4. Set duration: Choose how long the call should be. For discovery/qualification calls, 20-30 minutes is standard. For consultations, 30-60 minutes. Don't make it too long—you can always extend during the actual call.
5. Choose location: Select where the meeting happens:
   • Phone call: Calendly asks for their phone number, you call them
   • Zoom: Auto-generates a Zoom link (requires Zoom connection)
   • Google Meet: Auto-generates a Meet link (requires Google Calendar connection)
   • Custom: You provide instructions (e.g., "We'll call the number you provided")
6. Recommendation: Use Zoom or Google Meet for virtual calls. This gives you video option and auto-sends join links.
7. Configure availability: Set when people can book. Options:
   • Use your general availability (from account settings)
   • Set custom hours for this specific event type
   • Add date-specific overrides (block out vacation days)
8. Set booking windows: Control how far in advance people can book. Common settings: Minimum 4 hours notice (prevents same-day last-minute bookings), Maximum 60 days out (keeps your calendar manageable).
9. Add buffer time: Insert padding before/after meetings. Example: 15 minutes after each meeting gives you time to write notes and prepare for the next call.

Step-by-Step: Add Custom Questions

Custom questions collect additional information during booking. This is where Retell will prefill caller data:

1. In your event settings, find "Questions" section: This is usually a tab or section in the event editor.
2. Default questions (Name and Email): These are automatically included by Calendly. Don't remove them—Retell will prefill these.
3. Add custom question 1 - Company:
   • Click "Add Question"
   • Type: "One-line text" or "Short answer"
   • Question: "Company or Organization"
   • Required: Yes
4. Add custom question 2 - Use Case/Need:
   • Click "Add Question"
   • Type: "Multi-line text" or "Paragraph"
   • Question: "What do you need help with?"
   • Required: Yes
5. Optional: Add more questions: You can add budget, timeline, or other qualifier questions. Each additional question creates another prefill parameter.
6. Reorder questions: Drag questions to arrange them logically: Name, Email, Company, Need/Use Case.
7. Save your event: Click "Save" or "Save & Close".

Customizing Confirmation and Reminder Emails

Control what happens after someone books:

1. Find "Notifications and Cancellation Policy": In your event settings, look for email/notification section.
2. Confirmation email: This is sent immediately after booking. Calendly provides a default template—you can customize it with your brand voice and any prep instructions for the caller.
3. Reminder emails: Set when reminders go out. Recommended: 24 hours before (gives them time to reschedule if needed), 1 hour before (reduces no-shows).
4. SMS reminders: If you have a paid Calendly plan, enable SMS reminders. These have higher open rates than email.
5. Include meeting details: Ensure confirmation includes: Date/time with timezone, Join link (Zoom/Meet), Your contact info, Any prep work you want them to do.

Getting Your Calendly Scheduling Link

This is the base URL you'll use to generate prefilled links:

1. Go to your event: From Calendly dashboard, click on the event you just created.
2. Find "Copy Link": There should be a button or link icon to copy your scheduling URL.
3. Your link format: It will look like: https://calendly.com/yourhandle/discovery-call
4. Break down the URL:
   • https://calendly.com/ - Base domain
   • yourhandle/ - Your Calendly username or custom URL
   • discovery-call - Your event slug (based on event name)
5. Save this link: Copy it to your document from Module 1. You'll use it in Module 5 when setting up SMS.

What is URL Prefilling?

Prefilling uses URL parameters to automatically populate form fields. Instead of making the caller re-enter their name and email (which they just told the AI), we pass that data through the URL.

How it works: You add special parameters to the end of your Calendly URL. When someone clicks that link, Calendly reads the parameters and fills in the matching form fields. The caller just needs to pick a time slot.

Example:

Calendly Prefill Parameter Reference

Here are the parameters Calendly accepts:

• ?name= - Prefills the Name field (use full name with space)
• &email= - Prefills the Email field
• &a1= - Prefills the first custom question (your Company question)
• &a2= - Prefills the second custom question (your Use Case question)
• &a3= - Prefills the third custom question (if you added more)
• &a4= - Prefills the fourth custom question (if you added more)

Important syntax rules:

• First parameter uses ? (question mark)
• Subsequent parameters use & (ampersand)
• Spaces must be encoded as %20 (e.g., "Sarah Johnson" becomes "Sarah%20Johnson")
• Special characters should be URL-encoded (Retell handles this automatically)

Building Your Prefill Template

Let's create the template you'll use with Retell:

1. Start with your base link: https://calendly.com/yourhandle/your-event-name
2. Add the first parameter (Name): Add ?name={{Name}}
3. Add remaining parameters: Add &email={{Email}}&a1={{Company}}&a2={{UseCase}}

What are the {{brackets}}? These are placeholder variables that Retell will replace with actual caller data. When Retell sends the SMS, it automatically swaps {{Name}} with the actual name collected during the call.

Step-by-Step: Create Your Prefill URL

Now let's build your actual URL:

1. Take your Calendly link from the previous section: https://calendly.com/yourhandle/discovery-call
2. Add ?name={{Name}} to the end: https://calendly.com/yourhandle/discovery-call?name={{Name}}
3. Add &email={{Email}}: https://calendly.com/yourhandle/discovery-call?name={{Name}}&email={{Email}}
4. Add &a1={{Company}}: https://calendly.com/yourhandle/discovery-call?name={{Name}}&email={{Email}}&a1={{Company}}
5. Add &a2={{UseCase}}: https://calendly.com/yourhandle/discovery-call?name={{Name}}&email={{Email}}&a1={{Company}}&a2={{UseCase}}

Testing Your Prefill URL Manually

Before using it with Retell, test that prefilling works:

1. Create a test URL: Replace the {{variables}} with real test data:
   https://calendly.com/yourhandle/discovery-call?name=Test%20User&email=test@example.com&a1=Test%20Company&a2=Testing%20the%20prefill%20system
2. Note the %20: That's how spaces are encoded in URLs. "Test User" becomes "Test%20User".
3. Paste into browser: Copy your test URL and paste it into a new browser tab.
4. Verify prefilling: The Calendly page should load with Name, Email, Company, and Use Case already filled in.
5. Check all fields: Scroll through the form and confirm each field has the test data you provided.
6. Don't complete booking: No need to actually book a test appointment. Just verify the fields are populated.

If fields are blank: Check your custom question order in Calendly. a1 must be your first custom question, a2 must be your second. Reorder if needed and test again.

Common Prefill Issues and Solutions

Troubleshooting guide for when prefilling doesn't work:

• Issue: Fields are blank
  Solution: Check that parameter names match exactly. Name is case-sensitive. Should be ?name= not ?Name= or ?NAME=
• Issue: Custom questions not filling
  Solution: Verify custom question order in Calendly. First custom question is always a1, second is a2. Reorder if needed.
• Issue: Special characters break the URL
  Solution: Characters like &, ?, = in the data need URL encoding. Retell handles this automatically, but if manually testing, use a URL encoder tool.
• Issue: Name appears as "FirstnameLastname" with no space
  Solution: Ensure you're using %20 for spaces or + sign. Example: John%20Doe or John+Doe

End-to-End Test Checklist

Before moving to Module 3, verify all components are working:

1. Phone Number Test: Call your Retell number, confirm it rings and you hear a message (even if it's the default Retell message). Status: Working ✓
2. Business Hours Test: Check your phone number settings in Retell dashboard, verify hours are correct and timezone is right. Status: Configured ✓
3. Voicemail Test: Listen to your voicemail greeting in Retell dashboard to ensure it sounds professional. Status: Recorded ✓
4. Calendly Event Test: Visit your Calendly link directly, confirm it shows available time slots. Status: Accessible ✓
5. Prefill Test: Use your test prefill URL, verify all fields populate correctly. Status: Functioning ✓

What You've Accomplished

At this point, you have:

• A live phone number ready to receive calls
• Business hours configured so your agent knows when you're available
• Professional voicemail as a backup option
• A Calendly booking page configured with custom questions
• A prefill URL template ready to use with Retell

Your infrastructure is complete. In Module 3, we'll create the actual AI agent and connect it to this phone number.

Documentation for Your Records

Add these details to your Module 1 document:

Understanding Retell Agents

A Retell agent combines your system prompt, voice, language settings, and behavioral parameters. When calls come in, the agent processes speech-to-text, runs conversation through an LLM, retrieves from Knowledge Base, and converts responses to speech—all in real-time.

Step-by-Step: Create Agent

1. Navigate to Agents in Retell Dashboard
2. Click "Create Agent" or "+ New Agent"
3. Select "Single-Prompt Agent"
4. Name: "[Your Business] Receptionist"
5. Description: "Qualifies inbound calls"
6. Click Create

Step-by-Step: Add System Prompt

1. Find "System Prompt" field
2. Open your Module 1 document
3. Copy your complete System Prompt
4. Paste into Retell
5. Verify no [BRACKETS] remain
6. Save

Step-by-Step: Add Greeting

1. Find "Greeting" or "First Message" field
2. Paste greeting from Module 1
3. Keep 1-2 sentences (8-12 seconds)
4. Must include AI disclosure
5. Save

Select LLM Model

Choose the language model:

• GPT-4: Most capable. ~$0.09/min. Recommended.
• GPT-3.5-Turbo: Faster, cheaper ~$0.06/min. Good for simple scripts.
• Claude: Alternative, similar to GPT-4.

Use GPT-4 for best results following your prompt.

Step-by-Step: Choose Voice

1. Navigate to Voice section
2. Select provider: ElevenLabs (best quality)
3. Browse 30-50+ voices
4. Consider your brand:
   • Professional → mature, neutral
   • Creative → friendly, warm
   • Technical → clear, direct
   • Healthcare → calm, empathetic
5. Preview 3-5 voices with your greeting
6. Test business name pronunciation
7. Select and save

Voice Parameters

Stability (0.0-1.0):

• Recommended: 0.6-0.7
• Higher = consistent but monotone
• Lower = personality but unpredictable

Speed (0.8x-1.3x):

• Recommended: 1.0x-1.1x
• 1.0x = normal pace
• 1.1x = energetic

Fix Pronunciation

If voice mispronounces your business name:

• Use phonetic spelling: "Nwin" vs "Nguyen"
• Try different voices
• Use SSML tags (advanced)

Set Language

1. Find "Language" setting
2. Select "English (US)" for US/Canada
3. Choose regional variant matching your callers
4. Save

Interruption Handling

Controls how agent responds to interruptions:

• Low: Rarely stops. Good for noisy environments.
• Medium (Recommended): Natural conversations.
• High: Stops immediately. Can be choppy.

Step-by-Step: Configure Interruptions

1. Find "Interruption Settings"
2. Set sensitivity: Medium
3. Set delay: 800-1000ms
4. Resume: Listen and respond
5. Save

Step-by-Step: Configure Turn-Taking

1. Find "Turn-Taking" settings
2. Pause before response: 1.8-2 seconds
3. Silence timeout: 5-6 seconds
4. Enable filler word detection
5. Save

Step-by-Step: Create KB

1. Navigate to Knowledge Base
2. Click "Create Knowledge Base"
3. Name: "[Your Business] Info"
4. Description: "Services, pricing, FAQ"
5. Click Create

Step-by-Step: Upload Content

1. Open your KB
2. Click "Add Document"
3. Copy Module 1 KB document
4. Paste into Retell
5. Name: "Business Info v1"
6. Save (processing: 10-30 seconds)

Step-by-Step: Link to Agent

1. Return to agent configuration
2. Find "Knowledge Base" section
3. Click "Add Knowledge Base"
4. Select your KB
5. Save
6. Verify "Connected" status

Access Test Console

1. Save all agent settings
2. Find "Test Agent" button
3. Click to open console
4. Allow microphone access
5. Set audio output
6. Click "Start Call"

Test 1: Greeting

1. Start test call
2. Listen to greeting
3. Verify custom text
4. Verify voice clarity
5. Verify business name pronunciation
6. Respond: "I need [service]"
7. Verify agent begins qualification

Test 2: Full Qualification

1. Start new test
2. State need
3. Answer all 5 questions with test data
4. Verify all questions asked
5. Check transcript for accuracy

Test 3: Knowledge Base

1. Start new test
2. Ask: "What are your hours?"
3. Verify correct answer from KB
4. Ask: "What's your pricing?"
5. Verify correct answer
6. Ask off-topic: "What's the weather?"
7. Verify graceful handling

Test 4: Interruptions

1. Start test
2. Interrupt mid-greeting
3. Verify agent stops
4. Pause 3-4 seconds before answering
5. Verify agent waits
6. Say "Um... let me think..."
7. Verify agent doesn't interrupt

Troubleshooting

Agent doesn't hear me:

• Check microphone volume
• Verify browser permission
• Use Chrome browser
• Test in quiet room

Missing questions:

• Review system prompt
• Break questions into numbered list

No KB retrieval:

• Verify KB linked to agent
• Check KB processing complete
• Wait 1-2 minutes after upload

Robotic voice:

• Try different voice
• Adjust stability to 0.6-0.7
• Check internet connection

Module 3 Complete

• ✅ Agent created
• ✅ System Prompt added
• ✅ Greeting added
• ✅ Voice selected
• ✅ Language set
• ✅ Interruption handling configured
• ✅ Turn-taking configured
• ✅ KB created and uploaded
• ✅ KB linked to agent
• ✅ All 4 tests passed

What is Warm Transfer?

A warm transfer means the agent briefly speaks to YOU before connecting the caller. You hear a whisper message (the transfer whisper you wrote in Module 1) that gives you context about who's calling and what they need. Then you decide whether to accept or decline the transfer.

How warm transfer works:

1. Agent qualifies caller and determines they should be transferred
2. Agent says to caller: "Great, let me connect you now. One moment."
3. Agent puts caller on hold (caller hears hold music or silence)
4. Agent dials your phone number
5. You answer and hear the whisper: "Caller is Sarah from Acme Corp. Need: Website redesign. Urgency: 30 days. Budget: $10K. Okay to connect?"
6. You press 1 to accept (or 2 to decline)
7. If you accept: Caller is connected to you, agent drops off
8. If you decline: Agent returns to caller with fallback (booking link)

Why warm transfer is powerful:

• You know who you're talking to before the call starts
• You can mentally prepare your opening
• You can decline spam or unqualified callers without wasting time
• You can see the caller's need and urgency at a glance
• Professional experience for qualified callers—no awkward "So... why are you calling?"

Warm vs. Cold vs. Blind Transfer

Understanding the alternatives helps you appreciate warm transfer:

Blind Transfer (Don't Use): Agent transfers caller directly to you without warning. Your phone rings, you answer, caller is suddenly on the line. You have no context. This is jarring and unprofessional.

Cold Transfer: Agent tells caller "I'm transferring you now" and immediately connects. You answer and hear the caller, but no whisper or context. Better than blind, but you still start from zero.

Warm Transfer (Best): Agent briefs you first with whisper, you decide to accept or decline, then caller is connected. Professional, contextual, efficient.

For this course, we use warm transfer exclusively.

Prerequisites for Transfer Configuration

Before configuring transfer, ensure you have:

• Your transfer destination phone number (your mobile, office line, or team line)
• Your transfer whisper template from Module 1
• Your business hours configured from Module 2 (transfers only happen during these hours)
• Your agent created and configured from Module 3

Step-by-Step: Add Transfer Tool to Agent

Let's set up the transfer capability:

1. Open your agent: In Retell Dashboard, go to Agents and open the agent you created in Module 3.
2. Find "Tools" or "Actions" section: Look for a section labeled "Tools", "Actions", "Functions", or "Capabilities". This is where you add what your agent can DO (as opposed to what it knows or how it speaks).
3. Click "Add Tool": Look for a button to add a new tool or action.
4. Select "Transfer Call": From the list of available tools, choose "Transfer Call" or "Call Transfer".
5. You should now see transfer configuration options. We'll fill these in step by step.

Step-by-Step: Configure Transfer Type

Set the transfer to warm mode:

1. Find "Transfer Type" dropdown: This controls whether the transfer is blind, cold, or warm.
2. Select "Warm Transfer": Choose this option. The interface may also call it "Attended Transfer" or "Screened Transfer".
3. What this enables: You'll see additional fields appear for whisper message and accept/decline prompts.

Step-by-Step: Set Destination Number

Tell the agent where to transfer calls:

1. Find "Destination Number" or "Transfer To" field: This is where you enter your phone number.
2. Enter your number in E.164 format: This is the international standard format:
   • Start with + (plus sign)
   • Country code (1 for US/Canada)
   • Area code and number with no spaces or dashes
   • Example: +15551234567 (US number)
   • Example: +442071234567 (UK number)
3. Double-check the number: One wrong digit means transfers fail. Verify each digit.
4. Test format: Most Retell interfaces show a green checkmark if format is valid, red X if invalid.

Step-by-Step: Configure Transfer Whisper

Add the whisper message you'll hear:

1. Find "Whisper Message" or "Introduction Message" field: This is what YOU hear when your phone rings for a transfer.
2. Copy your Transfer Whisper from Module 1: Get the whisper template you created (e.g., "Caller is {Name} from {Company}. Need: {One-line Need}. Urgency: {Urgency Level}. Budget: {Budget Range}. Okay to connect?")
3. Paste into the field: Insert your complete whisper template.
4. Verify variable placeholders: Ensure the {curly bracket variables} are present. Retell will replace these with actual data from the qualification questions.
5. Map variables to collected data: Retell needs to know what {Name}, {Company}, etc. refer to. Most modern Retell interfaces auto-detect these if your system prompt asks clear questions. If there's a mapping section, link:
   • {Name} → "name" field collected during qualification
   • {Company} → "company" field
   • {One-line Need} or {Need} → "need" field
   • {Urgency} or {Urgency Level} → "urgency" field
   • {Budget} or {Budget Range} → "budget" field
6. Keep whisper under 20 seconds: Read your whisper aloud. If it takes longer than 20 seconds, trim it. You don't want to stand there listening to a 45-second briefing while the caller waits.

Step-by-Step: Configure Accept/Decline Prompts

Set what happens after you hear the whisper:

1. Find "Accept Prompt" or "Accept Instruction": This tells you how to accept the call.
2. Default is usually "Press 1 to accept": This works fine. Leave as default unless you have a reason to change.
3. Find "Decline Prompt" or "Decline Instruction": This tells you how to decline.
4. Default is usually "Press 2 to decline": This also works fine. Leave as default.
5. Alternative: Voice commands: Some Retell setups allow "Say 'accept' or 'decline'" instead of pressing buttons. Buttons are more reliable (less prone to transcription errors), so stick with button presses.

What happens when you press each button:

• Press 1 (Accept): Agent connects caller to you, agent exits the call, you and caller are now talking directly.
• Press 2 (Decline): Agent returns to caller and says something like "I'm unable to connect you right now. Let me send you a booking link instead." Agent then proceeds to booking fallback.
• No response (timeout): If you don't press anything within a certain time (usually 30 seconds), the transfer is treated as declined and agent falls back to booking.

Step-by-Step: Configure Human Detection

Set how the agent knows a human answered (vs. voicemail):

1. Find "Human Detection" or "Answering Machine Detection" setting: This controls how the system determines if the transfer destination was answered by a person or voicemail.
2. Enable Human Detection: Toggle this ON. Without it, the agent might try to whisper to your voicemail.
3. Set Detection Timeout: How long to wait while detecting. Recommended: 30 seconds. This gives your phone time to ring (most phones ring 4-5 times in 25 seconds) and the system time to analyze the answer.
4. Behavior on voicemail detection: If the system detects voicemail (e.g., you don't answer, call goes to your personal voicemail), it should:
   • Hang up (don't leave a message on your personal voicemail)
   • Return to caller
   • Proceed to booking fallback
5. Set this behavior: Look for "On Voicemail" or "Answering Machine Action" and select "Hang up and return to caller" or similar.

Why human detection matters: Without it, the agent might connect the caller to your personal voicemail, creating a confusing experience. Or worse, the agent plays the whisper to your voicemail, wasting the caller's time.

Step-by-Step: Set Transfer Timeout

Configure how long the system tries to connect:

1. Find "Timeout" or "Ring Duration" setting: How many seconds the agent will let your phone ring before giving up.
2. Recommended setting: 30 seconds: This allows 4-5 rings, enough time for you to pick up if you're nearby but not so long that the caller waits forever.
3. Consider your availability:
   • If you're always near your phone: 25 seconds is fine
   • If you sometimes step away but want a chance to run back: 35-40 seconds
   • Don't go above 45 seconds—callers get impatient
4. What happens on timeout: If timeout is reached (phone rang, no answer, no voicemail detected), the agent returns to caller and proceeds to booking fallback.

Step-by-Step: Configure Three-Way Announcement (Optional)

After you accept the transfer, you can have the agent make a brief introduction before exiting:

1. Find "Three-Way Message" or "Introduction Statement": This is optional. If available, it lets the agent say something to both you and the caller before dropping off.
2. Example three-way message: "Connecting you both now. [Your Name], this is [Caller Name] from [Company]."
3. Keep it brief: 1-2 sentences maximum. Example: "I'm connecting you both now."
4. Recommendation: Skip this for simplicity. You've already heard the whisper (with all the context you need), and the caller expects to be connected to you immediately. Adding a three-way announcement just delays the connection.
5. When to use it: Only if you want the caller to hear a formal introduction. Example: "I'm connecting you with [Your Name], our [Title]. One moment."

Complete Transfer Configuration Summary

Here's what your complete transfer setup should look like:

Understanding Booking Handoff

The booking handoff happens when transfer isn't possible or appropriate. The agent sends the caller your Calendly booking link and confirms they received it.

When booking happens:

• Transfer attempt failed (you didn't answer, voicemail detected, timeout)
• Call came in outside business hours
• Caller explicitly requested to book rather than transfer ("Can I just schedule a time?")
• You declined the transfer (pressed 2)

How booking works: The agent tells the caller "I'll send you a booking link right now via text and email." Then, in Module 5, we'll add SMS functionality so the link is actually sent. For now, we're configuring what the agent SAYS about booking.

Step-by-Step: Add Booking Logic to System Prompt

Ensure your agent knows how to handle booking:

1. Open your agent: Go to your agent configuration in Retell.
2. Review System Prompt: Scroll to the section where you defined transfer and booking logic.
3. Verify booking instructions exist: Your prompt should include something like:
   BOOKING FALLBACK - Send booking link if: - Transfer fails (no answer, line busy) - Outside business hours - Caller prefers to book rather than wait for transfer When sending booking link: 1. Tell caller: "I'll send you a booking link right now via text and email." 2. Confirm their email address is correct 3. Say: "The link will have your information already filled in. Just pick a time that works for you." 4. Ask: "Have you received the text?" (gives them a moment to check) 5. If yes: "Perfect. Looking forward to connecting with you." 6. If no: "Check your messages in a moment. You can also find it in your email."
4. If booking instructions aren't in your prompt: Add them now in the "BOOKING FALLBACK" section of your system prompt.
5. Save updated prompt: Ensure changes are saved.

Booking Conversation Flow

Here's what a booking handoff should sound like:

Email Confirmation Best Practice

Always confirm the email address before sending the link:

Why this matters: If the agent misheard the email during qualification (transcription error), the caller won't receive the booking link. By reading it back and getting confirmation, you catch errors before they cause problems.

How to confirm: The agent should say "Just to confirm, your email is [Email Address], correct?" and wait for the caller to confirm or correct.

Add this to your System Prompt if not already there:

Handling "I Didn't Get the Text" Scenarios

Sometimes callers don't receive the SMS immediately. Prepare for this:

Add to your System Prompt:

This ensures even if SMS fails (wrong number, carrier issues, etc.), the caller has multiple ways to book.

The Three Failure Scenarios

Your system must handle these three failure cases gracefully:

Scenario 1: Transfer Attempt Fails
Agent tries to transfer, your phone rings, but you don't answer (or voicemail picks up, or timeout is reached). Agent must immediately pivot to booking without making the caller feel abandoned.

Scenario 2: After Hours Call
Call comes in when you're unavailable (outside your configured business hours). Agent should not even attempt transfer—go straight to booking.

Scenario 3: Unqualified Caller
Caller doesn't meet your criteria (wrong service area, budget too low, spam, etc.). Agent should politely exit without transferring or booking. This isn't a "failure" per se, but still needs handling.

Step-by-Step: Configure Transfer Failure Handling

Set what happens when transfer doesn't work:

1. Find "On Transfer Failure" setting: This might be in your Transfer Tool configuration or in your agent's general settings.
2. Select action: "Continue Conversation": Don't hang up or error out. The agent should seamlessly continue talking to the caller.
3. Set fallback message: The agent should say something empathetic. Good examples:
   • "I tried to connect you, but [Your Name] is on another call right now."
   • "I wasn't able to reach [Your Name] at the moment."
   • "[Your Name] is currently unavailable."
4. Immediate pivot to booking: Right after the failure message, agent says: "Let me send you a booking link so you can choose a time that works for you."
5. Don't apologize excessively: One "I wasn't able to reach them" is enough. Don't make it sound like something went wrong—position booking as a normal, good alternative.

Step-by-Step: Configure After Hours Logic

Handle calls outside business hours:

1. Verify business hours are set: Double-check your phone number settings from Module 2. Hours must be configured for this to work.
2. Add after hours logic to System Prompt: Your agent needs to know not to attempt transfer outside hours:
   IF CALL IS OUTSIDE BUSINESS HOURS: Skip transfer attempt. Go directly to booking. Say: "Thanks for calling. We're currently outside office hours (we're available Monday-Friday 9am-5pm EST). Let me send you a booking link so you can schedule a time during our open hours." Then proceed with booking confirmation flow.
3. How Retell knows it's after hours: The platform automatically passes a flag to the agent indicating whether the call is within or outside configured hours. Your system prompt can reference this.
4. Alternative phrasing for after hours: You can be more casual: "I see you're calling after hours. Let me get you set up with a booking link..."

Step-by-Step: Configure Unqualified Caller Exit

Handle callers who don't meet your criteria:

1. Define disqualification criteria in System Prompt: Be specific about what makes someone unqualified:
   DISQUALIFICATION CRITERIA: - Budget below [your minimum] - Need does not match our services - Outside our service area - No timeline (just browsing) - Spam or sales calls If caller is disqualified: 1. Be polite and helpful 2. Suggest alternative: "For projects under $5K, I recommend [Alternative Resource]" 3. Offer to take message: "I can pass a message to the team if you'd like" 4. End call professionally: "Thanks for calling. Best of luck with your project."
2. Don't be rude or abrupt: Even unqualified callers might refer qualified ones. Stay professional.
3. Provide value if possible: If you can suggest where they should look, do so. Builds goodwill.
4. Don't waste time: Keep the exit brief. 30-45 seconds total.

Complete Failure Tree Diagram

Here's the complete logic flow with all failure handling:

Testing All Failure Scenarios

You need to test each path to ensure nothing breaks:

Test 1: Transfer Success

1. Use test console to qualify as a good lead
2. Agent attempts transfer (won't actually dial in test mode)
3. Simulate accepting transfer
4. Verify conversation transitions smoothly

Test 2: Transfer Failure (No Answer)

1. Qualify as good lead
2. Agent attempts transfer
3. Simulate no answer/timeout
4. Verify agent returns and offers booking
5. Check that transition is smooth (not abrupt or confusing)

Test 3: After Hours Booking

1. Temporarily adjust business hours in settings to make "now" outside hours
2. Start test call
3. Verify agent skips transfer attempt
4. Verify agent goes directly to booking
5. Reset business hours to correct times

Test 4: Unqualified Exit

1. Start test call
2. During qualification, give disqualifying answers (budget too low, wrong service area)
3. Verify agent politely declines and suggests alternatives
4. Verify agent doesn't attempt transfer or booking
5. Verify exit is professional

Final Configuration Verification

Before moving to Module 5, confirm everything is configured:

• ✅ Transfer Tool added to agent
• ✅ Transfer type set to Warm
• ✅ Destination number in E.164 format (+1...)
• ✅ Transfer whisper with {variables} configured
• ✅ Accept/Decline prompts set (Press 1/2)
• ✅ Human detection enabled
• ✅ Detection timeout: 30 seconds
• ✅ Ring duration: 30 seconds
• ✅ On voicemail: Hang up and return
• ✅ On timeout: Return to caller
• ✅ Booking logic added to System Prompt
• ✅ Transfer failure handling configured
• ✅ After hours logic configured
• ✅ Unqualified caller exit configured
• ✅ All four test scenarios passed

What's Next in Module 5

In Module 5, you'll:

• Enable SMS on your Retell phone number
• Add the Send SMS tool to your agent
• Configure the SMS message with your prefilled Calendly link
• Test SMS delivery during live calls
• Verify that booking links arrive with data prefilled

By the end of Module 5, callers will receive booking links via text message during the call, making the experience seamless and reducing no-shows.

How SMS Works in Voice Calls

Retell integrates SMS functionality so your agent can send text messages to callers during the conversation. The technical flow:

1. Agent collects caller's phone number (this is automatically captured from caller ID when they call in)
2. Agent triggers SMS send action during the call
3. Retell sends SMS via Twilio to the caller's phone number
4. Caller receives text within 2-5 seconds (typically while still on the call)
5. Caller can tap the link in the SMS and open your prefilled Calendly page

Why this is powerful:

• Instant delivery: Caller gets the link while you're still talking to them
• No transcription errors: Link is clickable—no typing required
• Confirmation in real-time: Agent can ask "Did you receive the text?" and verify
• Higher conversion: Studies show 3x higher booking rates when links are delivered via SMS during calls vs. sent after
• Works on any device: Desktop, mobile, tablet—all can receive and open SMS links

SMS Capabilities and Limitations

Understanding what SMS can and cannot do in this context:

What SMS can do:

• Send one-way messages from agent to caller during call
• Include text, links, emojis (use sparingly)
• Send multiple messages per call if needed
• Include dynamic content (caller name, company, custom links)
• Send to US, Canada, and 100+ international countries

What SMS cannot do in this setup:

• Receive replies from caller during the call (it's one-way outbound only)
• Send MMS (images, videos)—text and links only
• Guarantee delivery to landlines (works with mobile numbers only)
• Send to toll-free numbers (caller must be calling from a regular mobile/landline)

Cost: SMS costs approximately $0.0075-0.01 per message (less than 1 cent). For a typical call with one SMS sent, total cost is under $0.15 including voice minutes.

Prerequisites for SMS Setup

Before configuring SMS, ensure you have:

• Your Retell phone number from Module 2 (purchased and active)
• Your prefilled Calendly URL from Module 2 (with {{variable}} placeholders)
• Your agent configured from Module 3 and Module 4
• A mobile phone available for testing (you'll send a test SMS to yourself)

Understanding SMS Enablement

By default, phone numbers in Retell are voice-only. To send SMS, you need to enable SMS functionality on your specific number. This connects your number to Twilio's SMS infrastructure.

Two paths for SMS enablement:

• Retell-provided numbers: If you purchased your number through Retell (which we did in Module 2), Retell can enable SMS with a few clicks. This is the easiest path.
• Bring Your Own Number (BYON): If you're porting an existing Twilio number, you enable SMS directly in your Twilio account, then connect via Retell. More complex—not covered in this course.

We'll follow the Retell-provided number path since that's what we set up in Module 2.

Step-by-Step: Enable SMS on Your Number

Activate SMS functionality:

1. Navigate to Phone Numbers: In your Retell Dashboard, go to the Phone Numbers section from the left sidebar.
2. Select your number: Click on the phone number you purchased in Module 2. This opens the number's detail page.
3. Find "SMS Settings" or "Messaging" section: Scroll down to find SMS configuration. It might be labeled "SMS", "Text Messaging", "Advanced Add-ons", or "Capabilities".
4. Look for "Enable SMS" toggle or button: There should be a toggle switch or button to enable SMS functionality.
5. Click to enable: Toggle ON or click "Enable SMS" or "Setup SMS Function".
6. Confirm any prompts: You may see a confirmation dialog explaining SMS costs (usually $0.0075 per message). Confirm to proceed.
7. Wait for provisioning: SMS enablement usually takes 10-30 seconds. You should see a status change from "Provisioning" to "Enabled" or "Active".
8. Verify status: Confirm that your number now shows "SMS: Enabled" or similar indicator.

Troubleshooting SMS Enablement

Common issues and solutions:

Issue: "Enable SMS" button is grayed out or missing

• Cause: Your Retell plan may not include SMS, or the number type doesn't support SMS (some toll-free numbers have restrictions)
• Solution: Check your plan features in Account Settings. Upgrade if needed, or contact Retell support to enable SMS on your account

Issue: SMS enablement fails or stays in "Provisioning" status

• Cause: Twilio API connectivity issue or carrier restrictions
• Solution: Wait 5 minutes and refresh the page. If still provisioning, try disabling and re-enabling. If that fails, contact Retell support with your number

Issue: International numbers cannot enable SMS

• Cause: Some countries have different SMS regulations
• Solution: Check Retell's documentation for SMS availability by country. You may need to register your business with local carriers first

Understanding SMS From/To Routing

When SMS is enabled, here's what happens technically:

• From number: SMS will appear to come FROM your Retell phone number. This is the same number callers are calling. Consistency = trust.
• To number: SMS is sent TO the caller's phone number, automatically captured from their caller ID when they dial in.
• Caller ID capture: When someone calls your Retell number, the system automatically captures their phone number. This is stored as a variable the agent can use.
• Privacy note: Caller ID isn't always available (blocked numbers, some VoIP services). If caller ID is unavailable, SMS send will fail gracefully—agent should have a backup (reading the link aloud).

Understanding SMS Tools in Retell

Retell offers different ways to send SMS depending on your agent type:

• Single-Prompt or Multi-Prompt Agents: Use the "Send SMS" tool. This is a function your agent can call during conversation. The agent decides when to trigger it based on your system prompt instructions.
• Conversation Flow Agents: Use an "SMS node". You drag and drop an SMS node into your visual flow, and it sends the message when that node is reached.

Since we're using Single-Prompt (as chosen in Module 1), we'll configure the Send SMS tool.

Step-by-Step: Add Send SMS Tool

Add SMS sending capability to your agent:

1. Open your agent: Go to Agents in Retell Dashboard and open your agent from Module 3.
2. Navigate to Tools section: Find the "Tools", "Actions", or "Functions" section where you added the Transfer Call tool in Module 4.
3. Click "Add Tool": Look for the button to add a new tool or action.
4. Select "Send SMS": From the list of available tools, choose "Send SMS" or "Text Message".
5. Tool configuration panel opens: You should now see SMS-specific settings to configure.

Step-by-Step: Configure SMS From Number

Set which number sends the SMS:

1. Find "From Number" field: This specifies which phone number the SMS appears to come from.
2. Select your Retell number: Choose the phone number you enabled SMS on (your main Retell number from Module 2).
3. Format verification: Ensure it's in E.164 format (+1XXXXXXXXXX for US). Retell should auto-format this.
4. Why this matters: Using your main number ensures caller recognizes who's texting them. If you use a different number, they might ignore it as spam.

Step-by-Step: Configure SMS To Number

Set who receives the SMS:

1. Find "To Number" or "Recipient" field: This specifies who receives the SMS.
2. Use caller ID variable: You want to send to the person calling. Retell provides a variable for this, usually {{caller_number}} or {{from_number}} or {{phone_number}}.
3. Enter the variable: Type the exact variable name Retell uses (check their documentation or look for a variable reference in the UI). Common format: {{caller_number}}
4. Verify variable is supported: Most Retell interfaces show available variables. Confirm caller_number or equivalent is listed.
5. DO NOT enter a static number: Don't put your own number or a test number here—that would send every SMS to the same person. Use the variable.

Step-by-Step: Write Your SMS Message

Compose the text message with your booking link:

1. Find "Message" or "SMS Body" field: This is where you write the actual text of the SMS.
2. Start with a greeting: Personalize with the caller's name. Example: "Hi {{Name}},"
3. Add context: Briefly explain what this link is. Example: "Here's the booking link with your details filled:"
4. Insert your prefilled Calendly URL: Paste your complete prefilled URL from Module 2:
   https://calendly.com/yourhandle/your-event?name={{Name}}&email={{Email}}&a1={{Company}}&a2={{UseCase}}
5. Keep it concise: SMS has a 160-character recommended limit (though you can go longer). Aim for 2-3 short sentences plus the link.
6. No fluff: Skip marketing language. Just: Who, What, Link.

Character count for the example above: Approximately 120-150 characters depending on your URL length. This fits in one SMS and is concise.

Step-by-Step: Customize Your SMS Text

Adapt the template for your business:

1. Replace {{Name}}: This pulls from your qualification questions. Ensure your system prompt collects "name" and stores it properly.
2. Replace {{Email}}, {{Company}}, {{UseCase}}: Same—these must match the data collected during qualification.
3. Replace URL components:
   • yourhandle → your actual Calendly username
   • your-event → your actual event slug
4. Test variable spelling: Variables are case-sensitive. If your prompt stores "Name" (capital N), use {{Name}} not {{name}}. Match exactly.
5. Optional additions:
   • Add business name: "Hi {{Name}}, this is [Business Name]."
   • Add reassurance: "Just pick a time that works for you."
   • Add urgency (sparingly): "Book now to secure your spot."

Alternative SMS Message Formats

Here are variations based on tone and length:

Minimal (Shortest):

Standard (Recommended):

Detailed:

Professional Services:

Step-by-Step: Configure When SMS Is Sent

Tell your agent when to trigger the SMS:

1. Update System Prompt with SMS trigger logic: Your agent needs clear instructions about WHEN to send the SMS. Add this to your system prompt:
   WHEN TO SEND SMS: Send booking link SMS in these situations: 1. After qualification, if transfer fails or is declined 2. After qualification, if call is outside business hours (skip transfer, go straight to SMS) 3. If caller asks "Can you just text me a link?" HOW TO SEND SMS: 1. First confirm email address: "Just to confirm, your email is [email], correct?" 2. Then say: "Perfect. I'm sending you a text message and email right now with the booking link." 3. Trigger SMS send (use Send SMS tool) 4. Pause 2-3 seconds 5. Ask: "Have you received the text message?" 6. If yes: "Great! The link has your info already filled in. Just pick a time." 7. If no: "It should arrive in a moment. Check your email as well—I sent it there too."
2. Add SMS mention to booking fallback: Update your booking section from Module 4 to explicitly mention SMS sending.
3. Save updated System Prompt: Ensure all changes are saved in your agent configuration.

Complete SMS Tool Configuration Checklist

Verify your SMS tool is fully configured:

• ✅ Send SMS tool added to agent
• ✅ From Number: Your Retell phone number (SMS-enabled)
• ✅ To Number: {{caller_number}} or equivalent variable
• ✅ Message: Contains greeting, context, and prefilled Calendly URL
• ✅ Message includes {{Name}}, {{Email}}, {{Company}}, {{UseCase}} variables
• ✅ URL components replaced with your actual Calendly handle and event
• ✅ Message length under 160 characters (or acceptably short)
• ✅ System Prompt updated with SMS trigger logic
• ✅ System Prompt updated with SMS confirmation flow
• ✅ All changes saved

Why Testing SMS Is Critical

SMS testing verifies:

• SMS actually sends (not just configured, but functional)
• Caller receives the text within seconds
• Link in SMS is clickable
• Calendly page opens with prefilled data
• All variable substitutions work ({{Name}} becomes actual name)
• URL encoding is correct (spaces handled properly)

Without testing, you might launch with broken SMS, and callers won't be able to book.

Prerequisites for SMS Testing

Before testing, you need:

• Your agent fully configured (Modules 3, 4, and 5 complete)
• Your agent bound to your phone number (we'll do this in Module 6, but for SMS testing, you can use the test console)
• A mobile phone with SMS capability for receiving test messages
• Pen and paper to write down observations during testing

Test Method 1: Console Test (Simulated)

First, test in the Retell console to verify basic functionality:

1. Open test console: In your agent configuration, click "Test Agent" or "Test in Console".
2. Start test call: Begin a new test session.
3. Complete qualification: Answer the 5 qualification questions with test data. Use real-sounding data:
   • Name: John Smith
   • Company: Test Company
   • Need: Website redesign for product launch
   • Urgency: Need it within 30 days
   • Email: test@example.com
4. Trigger booking scenario: If the agent attempts transfer, simulate failure (don't answer). Agent should fall back to booking and SMS.
5. Listen for SMS mention: Agent should say "I'm sending you a text message and email right now..."
6. Check console logs: Retell's test console may show a log entry for "SMS Sent" or similar. Check for this indicator.
7. Note: In console testing, SMS may not actually be delivered (since there's no real caller number). You're verifying the agent triggers the action correctly.

Test Method 2: Live Phone Test (Actual SMS)

For real SMS testing, you need to call your Retell number from a mobile phone:

Important: To do this test, your agent must be bound to your phone number. We'll cover binding in Module 6, but here's how to do a quick bind for testing:

1. Quick bind (if not already done):
   • Go to Phone Numbers in Retell Dashboard
   • Click your number
   • Find "Bind to Agent" or "Inbound Agent" dropdown
   • Select your agent
   • Save
2. Prepare your mobile phone: Use a phone that can receive SMS. Not a landline, not a VoIP-only number.
3. Call your Retell number: From your mobile phone, dial the Retell number you purchased.
4. Complete the call flow:
   • Listen to greeting
   • Answer qualification questions (use test data)
   • If transfer is attempted, don't answer (let it fail to trigger booking)
   • Listen for agent to say "I'm sending you a text message now"
5. Check your phone for SMS: Within 5-10 seconds, you should receive a text message.
6. Verify SMS content:
   • From: Your Retell phone number
   • To: Your mobile phone number
   • Message: Contains greeting, context, and link
   • Variables: {{Name}} replaced with "Test User" (or whatever you said)
7. Tap the link: Click the Calendly URL in the SMS.
8. Verify Calendly page:
   • Page loads
   • Name field prefilled with "Test User"
   • Email field prefilled with "test@example.com"
   • Company field (a1) prefilled with "Test Company"
   • Use Case field (a2) prefilled with your stated need
9. Take screenshots: Capture the SMS received and the prefilled Calendly page for your records.

Troubleshooting SMS Test Issues

Common problems and how to fix them:

Issue: SMS not received at all

• Check 1: Verify SMS is enabled on your Retell number. Go to phone number settings and confirm "SMS: Enabled" status.
• Check 2: Confirm From Number in SMS tool is set to your Retell number (not blank, not a different number).
• Check 3: Verify To Number is {{caller_number}} variable, not a static number.
• Check 4: Check your mobile carrier—some carriers block automated SMS. Try a different phone.
• Check 5: Look in Retell call logs (we'll cover in Module 6). Find the call and check for SMS delivery errors.

Issue: SMS received but link doesn't work

• Check 1: Verify URL in SMS message is complete (starts with https://).
• Check 2: Check for line breaks in middle of URL (some SMS apps break long URLs incorrectly). If broken, shorten URL using a URL shortener or remove extra parameters.
• Check 3: Copy the link and paste into a browser manually to see if it works outside of SMS.

Issue: Calendly page opens but fields are blank (not prefilled)

• Check 1: Verify variable names in URL match what agent collected. If you collected "name" but URL says {{Name}}, capitalization might matter.
• Check 2: Check that qualification questions in system prompt actually store data. Agent might be asking questions but not storing responses.
• Check 3: Verify custom questions in Calendly match parameter order (a1 = first custom question, a2 = second).
• Check 4: Test prefilling manually using the test URL method from Module 2 to isolate whether issue is SMS or Calendly.

Issue: Some fields prefill, others don't

• Check 1: Verify which fields are blank. Usually it's custom questions (a1, a2) that fail while name/email work.
• Check 2: Reorder custom questions in Calendly to match your URL parameter order.
• Check 3: Check for typos in variable names in URL ({{Compnay}} instead of {{Company}}).

Issue: Variables not replaced (SMS shows {{Name}} literally)

• Check 1: Verify variable names match exactly what agent stores. Check system prompt for how data is stored.
• Check 2: Check Retell documentation for correct variable syntax. Some versions use ${variable} instead of {{variable}}.
• Check 3: Test with simpler variables first (just {{Name}}) to isolate which variables work.

Testing Different Scenarios

Test multiple scenarios to ensure robustness:

Scenario 1: Normal Booking Flow

• Qualify as good lead
• Transfer fails (don't answer)
• Agent sends SMS
• Verify: SMS arrives, link works, prefill correct

Scenario 2: After Hours Call

• Temporarily set business hours so current time is "after hours"
• Call in, qualify
• Agent skips transfer, goes straight to SMS
• Verify: SMS sent immediately without transfer attempt
• Reset business hours after test

Scenario 3: Caller with Special Characters in Name

• During qualification, give name with special characters: "O'Brien" or "García" or "Smith-Jones"
• Verify: SMS arrives, Calendly prefills correctly with special characters
• Tests: URL encoding of special characters

Scenario 4: Long Company Name

• Give a very long company name: "International Business Solutions and Technology Consulting Group LLC"
• Verify: SMS still sends, URL still works (even though it's long), Calendly prefills entire name

Best Practices for SMS Timing

When to send SMS during the call:

• Right after confirming email: "Just to confirm, your email is [email], correct?" → [They confirm] → "Perfect, sending the link now."
• Before you say goodbye: Don't send SMS and immediately hang up. Give caller time to receive and acknowledge it.
• Pause after triggering SMS: Agent should pause 2-3 seconds to give SMS time to be delivered before asking "Did you receive it?"
• Don't send multiple times: If caller says they didn't get it, don't spam them. Tell them to check email or repeat the URL verbally.

Handling "I Don't Have My Phone" Situations

Sometimes callers use office phones or don't have their mobile handy:

Add to your System Prompt:

SMS Compliance and Legal Considerations

Quick compliance notes:

• Implied consent: When someone calls your business number, they implicitly consent to receive transactional SMS (like booking links). You don't need separate opt-in for this.
• Transactional vs. Marketing: Booking links = transactional (allowed). Promotional messages = marketing (requires explicit opt-in). Don't send marketing via this system.
• Opt-out: Include "Reply STOP to unsubscribe" in your SMS if you plan to send follow-up messages. For one-time booking links, not required.
• International rules: Different countries have different SMS regulations. If serving international clients, research local laws (especially EU/UK with GDPR).

Module 5 Completion Checklist

Before moving to Module 6, confirm:

• ✅ SMS enabled on your Retell phone number
• ✅ Send SMS tool added to your agent
• ✅ From Number set to your Retell number
• ✅ To Number set to {{caller_number}} variable
• ✅ SMS message includes greeting, context, and prefilled Calendly URL
• ✅ All {{variables}} in URL match collected data
• ✅ System Prompt updated with SMS trigger logic
• ✅ Console test passed (agent triggers SMS)
• ✅ Live phone test passed (SMS received and works)
• ✅ Calendly page opens with prefilled data
• ✅ Screenshots captured for documentation
• ✅ Tested multiple scenarios (normal, after hours, special characters)

What's Next in Module 6

In the final module, you'll:

• Bind your agent to your phone number (if not already done)
• Run complete acceptance tests (all three scenarios: booked, transferred, fallbacks)
• Understand cost structure and budgeting
• Set up basic compliance (disclosure, recording, data handling)
• Review call logs and analytics
• Go live with your AI receptionist
• Monitor and optimize based on real calls

Understanding Agent Binding

Binding connects your agent to your phone number so incoming calls are answered by your agent instead of going to voicemail.

Step-by-Step: Bind Agent to Number

1. Navigate to Phone Numbers in Retell Dashboard
2. Select your phone number
3. Find "Inbound Agent" or "Bind Agent" dropdown
4. Select your agent
5. Click Save
6. Verify status shows "Bound to [Agent Name]"

Immediate Test After Binding

1. Call your Retell number from a different phone
2. Listen for your custom greeting (not generic Retell message)
3. Say "I need help with [service]"
4. Verify agent responds appropriately
5. Hang up

The Three Critical Test Scenarios

Scenario A: Successful Booking
Caller qualifies, agent sends SMS with booking link, caller receives prefilled Calendly page.

Scenario B: Successful Transfer
Caller qualifies, agent attempts warm transfer, you hear whisper, accept transfer, call connects.

Scenario C: Fallback Handling
Transfer fails or after-hours call, agent smoothly pivots to booking.

Scenario A: Successful Booking Test

1. Prepare test data: Name (Sarah Johnson), Company (Acme Corp), Need (Website redesign), Timeline (6 weeks), Budget ($8K-12K), Email (test email you can access)
2. From mobile phone, call your Retell number
3. Listen to greeting
4. State need: "I need help with website redesign"
5. Answer all 5 qualification questions with prepared data
6. Don't answer transfer phone (let it fail to trigger booking)
7. Listen for email confirmation
8. Confirm email is correct
9. Wait for SMS (should arrive in 5-10 seconds)
10. Confirm receipt when agent asks
11. End call
12. Open SMS and tap link
13. Verify Calendly page has all fields prefilled: Name, Email, Company, Use Case
14. Select time slot and complete booking
15. Cancel test booking from confirmation email

Scenario B: Successful Transfer Test

1. Prepare different test data: Michael Chen, TechStart Inc, Brand identity, 3 weeks, $6K
2. Have transfer phone ready and nearby
3. From test phone, call Retell number
4. Complete greeting and all 5 qualification questions
5. Agent announces transfer: "Let me connect you now"
6. Wait on hold
7. Transfer phone rings
8. Answer transfer phone
9. Listen to whisper with all caller data
10. Press 1 to accept
11. Verify call connects within 2-3 seconds
12. Test bidirectional audio (can hear each other)
13. Hang up both phones

Scenario C: Fallback Handling Test

Part 1: Transfer Failure

1. Use new test data: Lisa Martinez, GreenTech, UI/UX consulting, next month, $15K
2. Call Retell number
3. Complete qualification
4. Agent announces transfer
5. DON'T ANSWER transfer phone (let it ring out)
6. After 30 seconds, agent returns to caller
7. Verify smooth transition (no confusion)
8. Agent offers booking: "Let me send you a link instead"
9. Confirm email
10. Receive SMS
11. Verify link works and prefill correct

Part 2: After Hours Test

1. Temporarily adjust business hours to make "now" after hours
2. Call Retell number
3. Complete qualification
4. Verify NO transfer attempt (straight to booking)
5. Receive SMS and verify link
6. IMPORTANT: Reset hours to actual times

Retell AI Pricing Breakdown

1. Voice Agent Usage: ~$0.07-0.10 per minute (GPT-4: $0.09-0.10/min, GPT-3.5: $0.06-0.07/min)

2. Phone Number: Local ~$2/month, Toll-free ~$3-5/month

3. Inbound Call Minutes: ~$0.012-0.015 per minute (Twilio infrastructure)

4. SMS: ~$0.0075-0.01 per message

5. Platform Fee: $0 on pay-as-you-go (no monthly fee)

Real Cost Examples

Compare to alternatives: Virtual receptionist $300-800/month, Part-time human $1,500-2,500/month, Full-time $3,000-4,500/month

Monitoring Your Spending

1. Check Dashboard for current credit balance and usage
2. Set billing alerts at $20, $50 thresholds
3. Review usage weekly first month, then monthly
4. Typical small business: $20-50/month

AI Disclosure Requirement

You MUST disclose that callers are speaking with AI. Your greeting already includes "I'm the AI assistant" which satisfies this in most regions.

Call Recording Notice

Update greeting to include: "This call may be recorded."

Data You Should Never Collect

• Credit card numbers or payment info
• Social Security numbers or government IDs
• Medical/health information (HIPAA)
• Passwords or credentials
• Information about minors

Website Disclosure

Simple Compliance Checklist

• ✅ AI disclosure in greeting
• ✅ Recording notice in greeting
• ✅ System prompt prohibits sensitive data collection
• ✅ Website has AI disclosure
• ✅ Privacy policy updated
• ✅ Only sending transactional SMS (not marketing)

Soft Launch Strategy

1. Days 1-2: Add number to website and email signature only. Get 5-10 test calls in low-risk environment.
2. Days 3-5: Review call logs, make adjustments to system prompt based on real patterns.
3. Days 6-7: Add to Google My Business, social profiles, business cards.
4. Day 8+: Replace main number or forward to Retell. Full launch.

Understanding Call Logs

Retell Dashboard → Call Logs shows every call with:

• Call details: date, time, duration, caller number, outcome
• Full transcript: word-for-word conversation
• Call summary: auto-generated key points
• Actions taken: transfer, SMS, path followed
• Cost: how much this call cost
• Errors: any technical issues

Common Post-Launch Adjustments

Issue: Agent asks too many clarifying questions
Fix: Add to prompt: "Ask each question once. Don't ask follow-ups unless answer is completely unclear."

Issue: Callers repeat themselves
Fix: Add acknowledgment: "After caller answers, briefly acknowledge before next question. Say 'Got it' or 'Thank you'."

Issue: Agent misunderstands industry terms
Fix: Add terminology to Knowledge Base with definitions.

Key Metrics to Monitor

• Total calls: Volume received
• Average duration: Should be 2-5 minutes
• Transfer rate: 60-80% of qualified leads
• Booking rate: 80-90% of non-transferred
• Abandonment rate: Under 20% is good
• Cost per call: $0.25-0.40 for 3-4 min calls

Final Go-Live Checklist

• ✅ All three acceptance tests passed
• ✅ Agent bound to phone number
• ✅ Business hours correct
• ✅ Voicemail configured
• ✅ Transfer destination correct
• ✅ SMS enabled and tested
• ✅ Calendly prefill working
• ✅ AI disclosure in greeting
• ✅ Recording notice in greeting
• ✅ Website disclosure added
• ✅ Privacy policy updated
• ✅ Payment method added
• ✅ Know how to access call logs
• ✅ Soft launch plan ready

What You've Built

• ✅ Retell phone number receiving calls 24/7
• ✅ AI agent qualifying callers professionally
• ✅ Warm transfer with whisper context
• ✅ Automatic booking with prefilled Calendly
• ✅ SMS delivery during calls
• ✅ Business hours routing
• ✅ Complete fallback logic
• ✅ Legal compliance
• ✅ Cost-effective operation (~$20-50/month)

Skills You've Mastered

• AI architecture and agent types
• Conversation design and prompt writing
• Voice configuration and tuning
• System integration (Retell, Calendly, SMS)
• Transfer logic implementation
• Failure handling and fallback trees
• Testing methodology
• Compliance requirements
• Operations and monitoring

Next Steps

• Review 20-30 call transcripts first month
• Refine system prompt based on patterns
• Optimize call duration if over 5 minutes
• A/B test greeting variations
• Add custom responses for common objections
• Consider enterprise features at 200+ calls/month

Thank You

You've completed the Retell AI Mastery course. You now have a working AI receptionist that qualifies calls, transfers when appropriate, and ensures every caller gets a resolution.

Your AI receptionist is live. It's working for you 24/7.