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Automate Multi-Modal Appointment Booking via WhatsApp using GPT-4 and Cal.com

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Created by: Stéphane Bordas || stephanebordas

Stéphane Bordas

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Last update 3 days ago

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Who is this for?

This workflow is for healthcare professionals, consultants, coaches, and service businesses who want to completely automate their appointment booking system via WhatsApp — without manual intervention for reservations, availability checks, or cancellation management.

What problem is this workflow solving? / Use case

Managing appointments manually via WhatsApp is extremely time-consuming: checking availability, confirmations, rescheduling, cancellations. This workflow automates the entire process — from initial request to final confirmation — allowing your clients to book, modify, or cancel appointments 24/7, in natural language, directly via WhatsApp.

What this workflow does

  • Processes multi-modal messages (text, audio, images) from WhatsApp Business API
  • Detects message type and routes to appropriate processing (Whisper for audio, GPT-4 Vision for images)
  • Uses AI Agent with 5 Cal.com tools to manage complete appointment lifecycle
  • Checks real-time availability in your Cal.com calendar
  • Books appointments autonomously without human intervention
  • Handles cancellations and rescheduling requests
  • Maintains conversation context with Simple Memory for natural exchanges
  • Formats responses with Unicode bold for better WhatsApp readability
  • Sends automated replies directly to the client

The result: a fully automated 24/7 appointment management system via WhatsApp.

Setup

1. WhatsApp Business API

  • Connect your WhatsApp Business API account in n8n.
  • Set up the webhook in Facebook Developer Console (Webhook → Messages → Subscribe).
  • Add your phone_number_id and access token credentials.

2. Cal.com

  • Create a Cal.com account and configure your calendar.
  • Generate an API Key from Cal.com settings.
  • Set up your event types (duration, availability, pricing).
  • Add your Cal.com API credentials in n8n.

3. OpenAI

  • Get an OpenAI API key (for GPT-4, Whisper, and Vision).
  • Add your OpenAI credentials in n8n.
  • The workflow uses GPT-4 for conversation, Whisper for audio transcription, and GPT-4 Vision for image analysis.

4. Customize the AI Agent

  • Edit the System Message to define your agent's personality, tone, and business context.
  • Adjust timezone in tool parameters (default: Europe/Paris).
  • Configure event type IDs for different appointment types.

5. Test & activate

  • Test with different message types (text, audio, image) from WhatsApp.
  • Verify appointments are created correctly in Cal.com.
  • Switch to production mode and activate the workflow.

This workflow helps you build a fully autonomous AI booking assistant, transforming WhatsApp into a 24/7 appointment management system.


Need help customizing?

Contact me for consulting and support: LinkedIn / Youtube