1 <= lengthUsed only when from_uid is empty.
1 <= lengthuint80 <= value <= 255Optional; an empty value disables idempotency lookup.
uint80 <= value <= 255uint320 <= value1 <= lengthA non-empty array selects request-scoped delivery, requires an empty channel_id, and requires sync_once.
Any non-zero value means true.
0Any non-zero value means true.
0