idempotencyKey property
IdempotencyKey makes a retry safe: the same key never charges twice, it replays the first result. Sending one is strongly recommended for an agent, which retries by construction. Empty falls back to a windowed key derived from the amount and currency, so a double-submit inside 15 minutes still collapses onto one charge.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? idempotencyKey;