> ## Documentation Index
> Fetch the complete documentation index at: https://docs.retellai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Book Calendar

> Connect Cal.com to a Retell voice agent so callers can book appointments mid-conversation — set up event types, API keys, and the booking tool step by step.

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.

<Frame>
  <img height="300" src="https://mintcdn.com/retellai/zL2HeUqUnagEN9eK/images/c_1.png?fit=max&auto=format&n=zL2HeUqUnagEN9eK&q=85&s=8d2a777c77fcd3e4810b18e6ccdd860e" alt="Check availability tool interface" data-path="images/c_1.png" />
</Frame>

<Steps>
  <Step title="Create a Cal.com Account">
    1. Visit [cal.com](https://cal.com) to create an account
  </Step>

  <Step title="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
  </Step>

  <Step title="Obtain Required Credentials">
    <Frame>
      <img height="300" src="https://mintcdn.com/retellai/zL2HeUqUnagEN9eK/images/c_2.png?fit=max&auto=format&n=zL2HeUqUnagEN9eK&q=85&s=b75d1234c8bef4373942fe6b02c01ff5" alt="API credentials location" data-path="images/c_2.png" />
    </Frame>

    #### 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

    #### 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
  </Step>

  <Step title="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
  </Step>

  <Step title="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.
    ```
  </Step>
</Steps>

Video tutorial (based on single / multi prompt agent):

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