# Christoph Hartmann – Cal.com booking page

> Christoph is the founder of the AI productivity startup https://donethat.ai. He has over fifteen years experience in AI, including a PhD, a stint at BCG, and as a CTO for a scale-up. Next to this, he writes about elements of a good life at https://euzoia.org. Personal website: https://heychristoph.com. Side-project on agents: https://botacts.com

Booking page: https://cal.com/christoph-cal

## Event types

- [15 min meeting](https://cal.com/christoph-cal/15min): 15 min, confirmed instantly, event type id 5282388. Details: https://cal.com/christoph-cal/15min.md
- [30min meeting](https://cal.com/christoph-cal/secret): 30 min, confirmed instantly, event type id 5282387. Details: https://cal.com/christoph-cal/secret.md

## Check availability

```http
GET https://api.cal.com/v2/slots?eventTypeId=<event type id>&start=YYYY-MM-DD&end=YYYY-MM-DD&timeZone=<IANA time zone>
cal-api-version: 2024-09-04
```

The response is `{"data":{"YYYY-MM-DD":[{"start":"<ISO 8601 with offset>"}]}}`; no API key is needed.

## Book

Each event type's `.md` document lists its required booking fields and the `POST https://api.cal.com/v2/bookings` request (`cal-api-version: 2026-02-25`).

## More

- API docs: https://cal.com/docs/api-reference/v2/introduction