Written by Hector Garcia
@hex.garEstimated reading time: 12 min read
AI receptionist agent: full build guide
AI Consultant
SystemsReading time: 12 min read
This agent answers your business phone line, checks your real calendar for open times, books the appointment, and answers questions straight from your own service menu. Built with the ElevenAgents feature in ElevenLabs, it works for any service based business, the massage studio used throughout this guide is just the example. Start with a free ElevenLabs account, then follow each step in order.
What happens on a call
The agent greets the caller, sorts the call into a new booking, a reschedule or cancel, or a question, then moves straight into handling it.
For a booking it checks real open slots on your calendar, offers two real times, confirms the caller's name and number, books it, and reads the confirmed details back before ending the call.
Before you start
Setup steps
- Sign up at try.elevenlabs.io and open the ElevenAgents section
- Create a new agent and name it after the business it answers for
- Write the first message, a short front desk style greeting, not a menu
- Paste the system prompt below into the agent's instructions, then fill in the bracketed parts
- Add your knowledge base document under the agent's Knowledge Base tab
- Pick a voice under the Voice tab and preview a few over a phone call before deciding
- Connect your Google Calendar directly under the agent's Tools tab, ElevenAgents includes googlecalendarcheckavailability and googlecalendarcreateevent built in, no separate automation tool needed
- Connect a phone number under the Phone Numbers tab in your ElevenLabs dashboard, provisioned directly or through Twilio
- Call the number yourself and test a normal booking, a reschedule request, and a random question outside the knowledge base
- Confirm the closing line actually triggers the end_call tool, otherwise the agent keeps the line open after saying goodbye
- Check whether your area requires telling callers they are speaking with an AI or that the call may be recorded
- Go live once every test case behaves the way you expect
Copy paste templates
Paste the system prompt into the agent's instructions, and the knowledge base document under the agent's Knowledge Base tab. Fill in the bracketed parts for your business. A version filled in for the massage studio used in the demo follows the blank template.
Booking assistant system prompt
You are [Agent Name], a warm and efficient booking assistant for {{business_name}}, a {{business_type}}. Your only goal on this call is to help the caller book, reschedule, or get answered on a service question, then get them off the phone quickly and confirmed.
Personality: warm, calm, unhurried but efficient. Talk like the front desk person who actually likes the job, not a call center script. Short sentences. Never sound like reading options off a menu.
Conversation flow:
1. Greet and ask what they need. Listen for one of three intents: new booking, reschedule or cancel, or a question.
2. New booking: ask what service they are looking for. Match it against the services listed in your knowledge base. Call google_calendar_check_availability to see real open times, then offer two real slots from what it returns. Confirm the caller's name and best number to text a reminder to. Call google_calendar_create_event with the confirmed name, service, and chosen time. Repeat the full booking back using exactly what the tool confirms.
3. Reschedule or cancel: tell them a team member will call back within the day to handle it, do not guess at existing bookings.
4. Question about pricing, services, or policy: answer only from your knowledge base. If it is not in there, especially anything sensitive like health, safety, or liability, say a team member will follow up before their appointment, never guess.
5. If they ask for a discount or a price you do not have, do not invent one. Offer to note it for a callback instead.
6. Keep the call under 90 seconds unless they are actively working through booking details.
Hard rules:
- Never invent a price, service, or available time slot. Prices and services come from the knowledge base, availability comes only from google_calendar_check_availability.
- Never give advice outside your knowledge base. Always defer sensitive topics, health, safety, legal, or liability, to a human team member.
- Never claim to be human if asked directly.
- If asked to stop calling or texting, comply immediately.
- Always confirm the final booking details out loud before ending the call, using exactly what google_calendar_create_event confirms back to you.
7. Once the closing line is said and the caller has nothing else, say a brief goodbye and immediately call the end_call tool. Do not wait for them to hang up first, and do not keep talking after the goodbye line.Knowledge base template
[BUSINESS NAME] SERVICE MENU AND POLICIES ABOUT What the business does and who it serves. This document is the source of truth, the agent should not answer with anything not listed here. HOURS Days and hours open, days closed. SERVICES AND PRICING Every service you offer, one fixed duration per service if possible, it keeps booking logic simple. PAYMENT How payment is collected, what methods are accepted. CANCELLATION POLICY What happens if a client cancels late or does not show. LATE ARRIVAL What happens if a client arrives late. SENSITIVE TOPICS Anything the agent should never answer directly, health, safety, legal, or liability related, and what to say instead. LOCATION Address and parking notes. CONTACT FOR ESCALATIONS What the agent should say when a request falls outside this document.
Example: massage studio knowledge base
BLOOM MASSAGE STUDIO SERVICE MENU AND POLICIES ABOUT Bloom Massage Studio is a boutique massage and wellness studio. We offer therapeutic and relaxation massage services by licensed massage therapists. This document is the source of truth for pricing, services, and policies. Do not quote anything not listed here. HOURS Tuesday to Saturday, 9:00am to 6:00pm Closed Sunday and Monday SERVICES AND PRICING Swedish Massage (relaxation, light to medium pressure) 60 minutes: $95 Deep Tissue Massage (firm pressure, targets muscle tension) 60 minutes: $110 Hot Stone Massage (heated stones combined with massage) 60 minutes: $105 Prenatal Massage (safe for 2nd and 3rd trimester only) 60 minutes: $105 Couples Massage (two therapists, side by side rooms) 60 minutes: $220 total Add ons Aromatherapy: $15 Scalp treatment: $20 PAYMENT We accept credit card, debit card, and Apple Pay. Payment is collected at the end of the session. A card on file is required to hold any booking. CANCELLATION POLICY Cancellations made more than 24 hours before the appointment are free. Cancellations inside 24 hours or no shows are charged 50 percent of the service price to the card on file. LATE ARRIVAL If a client arrives more than 15 minutes late, the session may be shortened to protect the next appointment, and full price still applies. SENSITIVE TOPICS Prenatal massage is only available starting the 2nd trimester, first trimester requests get a callback. No massage on clients with a fever, contagious illness, or open wounds in the treatment area. Any medical condition, injury, medication interaction, or pregnancy risk question gets escalated to a licensed therapist by callback, never answered directly. LOCATION 1420 Bloom Avenue, Suite 2, San Diego, CA 92101 Free parking available behind the building. CONTACT FOR ESCALATIONS If a request falls outside this document, tell the caller a team member will follow up by text or call within the day. Do not guess or improvise pricing, services, or medical guidance.