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

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