executionMode property
ExecutionMode is one-shot or long-running, and it decides who may start this agent. one-shot runs only when something POSTs to it; long-running is additionally invoked by the scheduler on Schedule, once a minute against the cron. An org's long-running agents are capped, so a switch INTO it can be refused with 409.
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? executionMode;