- REST: send it in
Idempotency-Key. - MCP: pass it as
client_request_idin tool arguments. - REST helper: set
client_request_idin the request document.
idempotency_conflict means an identifier was reused with different input. idempotency_in_progress means an earlier request is still being handled. Honor Retry-After when present; do not create another job to work around either response.
A timeout or connection loss does not prove the server rejected the request. Keep a durable mapping from your local task to its mutation identifier and returned job ID.