This guide explains how to integrate cal.com’s book appointment functionality into your application. This integration allows you to book appointments on cal.com.
Check availability tool interface
1

Create a Cal.com Account

  1. Visit cal.com to create an account
2

Configure Event Type

  1. Navigate to the “Event Types” section in your cal.com dashboard
  2. Click “New”
  3. Configure your event settings
  4. Click “Save” to create the event type
3

Obtain Required Credentials

API credentials location

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Get Event Type ID

  1. Open your created event type
  2. Look at the URL in your browser
  3. The event type ID is the number in the URL Example: https://app.cal.com/your-username/event-type/1427703 In this case, 1427703 is your event type ID

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Get API Key

  1. Go to “Settings” in your cal.com dashboard
  2. Navigate to “Developer” section
  3. Click on “API Keys” to retrieve your API key
4

Add a book on calendar function in Retell

  1. Enter the following details:
    • Tool name: this has to be unique within that agent
    • API Key from cal.com
    • Event Type ID
    • Tool description (example: “Book the appointment for 30-minute consultation calls”)
    • (optional): add a timezone to be used in the function
  2. Click “Save” to complete the setup
5

Update prompt for function

It’s best to include in the prompt explicitly when is the best time to invoke the custom function. For example:
When user selected a slot, please book the appointment by calling the `book_appointment` function.
Video tutorial (based on single / multi prompt agent):