Create or update a booking from your system

One request per booking. Repeating the same external_id updates the booking instead of creating a second one; a new start_at is a reschedule (reminders are re-planned, the confirmation is not sent again). status: "cancelled" cancels.

start_at without an offset (2026-09-23 15:00) is read in the project's time zone; the response returns it back as start_at_local so you can check how it was understood. Messages follow the project's settings (Automations → Bookings) and go out between 9:00 and 21:00 project time. The platform writes first only to contacts the WhatsApp number already knows. contact in the response is a hint, re-checked at send time: known (messages go out), unknown (never written to first, the booking is still kept), unverified (the check could not answer yet, the platform retries) or instagram (a 24h reply window, reminders do not fit). Requires a key with the write scope.