How do I identify a webhook event and know whether it is final?

Every webhook payload carries an __event__ object with the event type, for example BusinessSearch.completed or LiensSearch.failed, plus the origin of the request. Use the type to route the payload.

For events about a request object, the payload also carries the object’s own state: COMPLETED on a completed event, FAILED on a failed event, and EXECUTING when work is still in progress. Check the state rather than assuming from the event name.

The payload body is the same shape as the corresponding GET response, so a completed webhook gives you everything a fetch would.