Idempotency

Every state-changing request must carry a unique Idempotency-Key header (a UUID). Replaying the same key returns the original result instead of creating a duplicate.

• The key is required; omitting it is a 400 invalid_request.
• A key is released back to you when the request is refused before the service runs (for example a wrong-typed field or a missing required URL), so you can fix the payload and retry with the same key.
• A key is consumed once the request reaches the service; a later replay with the same key returns the first outcome.