I needed to reread this sentence about the empty payload a few times to understand it because of the all/only combination. Recommend being more explicit about the intentional lack of payload.

Existing Wording:

With the content type of empty, all information about the resources involved in triggering the notification is only available via channels other than the Subscription itself (e.g., the REST API).

Proposed Wording:

With the content type of empty, triggering resource details are not available via the subscription channel.

(Comment 37 - imported by: Gino Canessa)