Create a booking through the Cal.com API v2 after validating slot availability
domain: cal.com · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Call GET /v2/slots with the eventTypeId (or eventTypeSlug/username) and a date range to retrieve currently available start times.
Confirm the desired start time is present in the returned slots before attempting to book it, rather than assuming any arbitrary time is bookable.
POST /v2/bookings with the chosen start (ISO timestamp), eventTypeId, and an attendee object containing name, email, and timeZone.
Include any required custom booking-question responses in the responses field — omitting a required field returns a 400 error_required_field response.
Handle the booking response's status and id to support later reschedule/cancel calls against that specific booking.
Known gotchas
Slots returned by GET /v2/slots can go stale between the availability check and the booking POST under concurrent load — be ready to handle a booking rejection due to a race and re-check availability.
For round-robin or collective event types, availability is derived per-member from each host's own schedule, so a slot valid for one host lineup may not be reproducible if the API's host-assignment logic differs from what you expect client-side.
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