Book Cal.com meetings from ElevenLabs voice agent conversations

This is a specific use case. The [ElevenLabs guide for Cal.com bookings](https://elevenlabs.io/docs/conversational-ai/guides/integrations/cal-com) is comprehensive but I was having trouble with the booking API request. So I built a simple workflow to validate the request and handle the booking creation.

Who's this for? You have an ElevenLabs voice agent (or other external service) booking meetings in your Cal.com account and you want more control over the bookmeeting tool called by the voice agent.

How's it work? Request is received by the webhook trigger node Request sent from ElevenLabs voice agent, or other source Request body contains contact info for the user with whom a meeting will be booked in Cal.com Workflow validates input data for required fields in Cal.com If validation fails, a 400 bad request response is returned If valid, meeting is booked in Cal.com api

How do I use this? Create a custom tool in the ElevenLabs agent setup, and connect it to the webhook trigger in this workflow. Add authorization for security.  Instruct your voice agent to call this tool after it has collected the required information from the user.

Expected input structure Note: Modify this according to your needs, but be sure to reflect your changes in all following nodes. Requirements here depend on required fields in your Cal.com event type. If you have multiple event types in Cal.com with varying required fields, you'll need to handle this in this workflow, and provide appropriate instructions in your voice agent prompt.

"body": { "attendeename": "Some Guy", "start": "2025-07-07T13:30:00Z", "attendeephone": "+12125551234", "attendeetimezone": "America/NewYork", "eventTypeId": 123456, "attendeeemail": "someguy@example.com", "attendeecompany": "Example Inc", "notes": "Discovery call to find synergies." }

Modifications Note: ElevenLabs doesn't handle webhook response headers or body, and only recognizes the response code. In other words, if the workflow responds with 400 Bad request that's the only info the voice agent gets back; it doesn't get back any details, eg. "User email still needed".

You can modify the structure of the expected webhook request body, and then you should reflect that structure change in all following nodes in the workflow. Ie. if you change attendeename to attendeeFirstName and attendeeLastName then you need to make this change in the following nodes that use these properties. You can also require or make optional other user data for the Cal.com event type which would reduce or increase the data the voice agent must collect from the user.