# description
The synchronous rejection body returned when a responding NP exercises its protocol-level agency to decline engagement for policy-governed reasons — insufficient caller trust, capacity limits, scheduled inactivity, or general refusal — without an underlying exception in the received message. The caller MUST NOT expect an on_* callback.

NackDiscretionary appears as the response body for 403 responses on action endpoints. The responding NP produces it; the calling NP MUST treat it as a terminal response for the current request. NFOs MAY restrict or prohibit discretionary NACKs for specific actions, domain contexts, or transaction lifecycle stages per CON-008-20 in NFH-008.

Relationship: Extends the Ack schema with status constrained to NACK and adds an error field whose code MUST be one of the POL_ENGAGEMENT_* discretionary refusal codes.