Optional Idempotency-Key on POST and PUT

For selected POST and PUT operations across the Accounts API (not limited to a single endpoint), you may send an Idempotency-Key header so that safe retries (for example timeouts or network errors) do not perform the operation twice when you retry with the same key and same body.

• If you omit the header: The request is processed as usual with no idempotency behavior.
• If you send it: Retries with the same key and payload should receive the same HTTP status and body as the first completed attempt; the API may indicate a replay when applicable.

See the Idempotent requests guide and the API reference for which operations support the header, key format, TTL behavior, and error cases (such as a conflicting payload for the same key).