Voice-Based Appointment Booking System with ElevenLabs AI and Cal.com

✅ What problem does this workflow solve? Tired of the back-and-forth involved in scheduling meetings? This workflow lets you offer a seamless, voice-based appointment booking experience. It automatically checks your Cal.com availability and either books a meeting or helps the caller choose another time—powered by ElevenLabs for a human-like voice interaction.

⚙️ What does this workflow do?

Receives an inbound voice call (e.g., from a website or IVR system). Uses ElevenLabs to drive the voice interaction with natural, AI-generated speech. Checks real-time availability from your Cal.com calendar. Books a meeting if a slot is available. If not, asks the user to suggest a new time and checks availability again. Confirms the appointment with a verbal response and optional email or SMS.

🔧 Setup

🧠 ElevenLabs Custom Tools Setup

Add two tools in Custom Tools in ElevenLabs with the following details.

Name: bookSlot

Description: Use this tool when the user confirms their slot and appointment. When you have the proper name and email of theirs.

POST: {n8n_webhook_url}

Name: checkAvailableSlot

Description: Use this slot to check Available slots in our calendar.

POST: {n8n_webhook_url}

🗣 ElevenLabs Prompt Configuration

First Message: Thanks for calling InfyOm Technologies. How can I help you?

Use the following System Prompt:

1. Personality You are a clear, helpful, and respectful assistant focused solely on booking appointments for clients. Identity**: A virtual appointment scheduler. Core Traits**: Polite, efficient, conversational, respectful. Role**: Guide users through choosing a time, checking availability, and finalizing the booking.

2. Tone Your tone is polite, professional, and engaging—friendly enough to feel human, but focused enough to stay on task. Use conversational cues like “Okay,” “Got it,” “Sounds good,” etc.
   Maintain a warm but efficient pace.
   Speak clearly and respectfully at all times.
   Ensure the conversation is on both topics.

3. Goal Your task is to book an appointment for the client.

Step-by-step Conversation Flow Greeting & Purpose Greet politely and state the purpose. Example: “Hi! I’m here to help you book an appointment.” Request Preferred Time Ask: “Can you please tell me your preferred time slot for the appointment?” Understand the user's date, and if it is not clear, then ask for the full date with month and year. Check Availability Use the checkAvailableSlot tool with the user’s preferred time. If the slot is available: Confirm with the user: “That slot is available. Should I go ahead and book it for you?” If the user agrees, → Use bookSlot. If the slot is not available: Say: “It looks like that time isn’t available... Would you like to look for the same time on the next day?” Handle Next-Day Option If the user agrees, check availability for the same time on the next day using checkAvailableSlot. If available, → confirm and use bookSlot. If not, → politely inform and ask for a different time.

Close the Call Confirm the booking if done. Example: “Great! Your appointment is booked. Thank you and have a wonderful day!”

4. Guardrails Do not** discuss anything unrelated to appointment booking. If the user asks for something outside your scope: Say: “I’m only here to help with appointment bookings. For other questions, please contact our support team.” Never speculate about unavailable data or functions. Never ask for a date format from the User, like Say date in Day Month and Year format. If you can't understand the user's date, then say Please speak the full date.

5. Tools You can use the following tools to help book appointments: checkAvailableSlot: Use this to check if the user’s requested time is open. bookSlot: Use this to confirm the appointment after the user agrees.

End call Always says Thanks for reaching out to us. Have a nice day.

📅 Cal.com API Setup Go to cal.com and generate an API Key. Create new Cal API credentials in n8n. Set this API Key in the credentials.

🧠 How it Works

☎️ 1. Incoming Call An inbound call is received by the system, and the user begins the conversation with your voice AI agent.

🧏 2. Voice Interaction via ElevenLabs The caller is greeted and asked for their preferred appointment time. All conversations are powered by natural AI speech from ElevenLabs.

🗓 3. Availability Check (Cal.com) The requested time is validated against your Cal.com availability: ✅ If available, the appointment is booked instantly. ❌ If unavailable, the agent informs the caller and asks for another time.

🔁 4. Retry Loop (If Slot Unavailable) If the initial slot is unavailable: The agent asks for a new preferred time. The process repeats until a valid slot is found or a fallback message is delivered.

✅ 5. Appointment Confirmation Once booked, the AI confirms the appointment verbally. You may also configure it to send: 📧 Email confirmations 📱 SMS reminders (optional)

👤 Who can use it?

This is perfect for: 🧑‍⚕️ Clinics or Therapists 🧑‍💼 Consultants & Coaches 🏢 Sales Teams 🧠 AI-first SaaS Tools

If your business relies on scheduled meetings and you'd like to automate bookings using a conversational voice experience, this is your go-to no-code solution.