# description
The synchronous rejection body returned when the requested resource does not exist in the system.

NackNotFound appears as the response body for 404 responses. The implementing actor produces it; the calling actor MUST NOT retry without correcting the resource identifier.

Relationship: Extends the Ack schema with status constrained to NACK and adds an error field describing why the resource was not found.

# properties.message.properties.messageId.description
Echoes the messageId from the triggering request's Context, for caller correlation.