Idempotency-Key of 16–128 printable non-space characters. Generate one per intended search and reuse it with the identical body on retries. MCP requires client_request_id and uses it for the same purpose.
If a request times out, accepted work may still be running. Retry the same request and identifier rather than creating a new billable search. Changing input with an existing key returns idempotency_conflict. Keep retries within a bounded deadline and honor Retry-After.