Protocol messages make Agent action governable
What Agents send, what Relay checks, and what the receipt returns
Envelope fields
Every message needs attribution, factor context, receipt, and trace
FieldMeaningUseBoundary
Actor ref
Who is acting
Names the Agent and capability version
Attribution
Proposed action
What may happen
States type, object, requested outcome, policy, and risk
No execution
Evidence refs
What supports it
Points to evidence without private payloads
Ref only
Decision factors
What Relay checks
Identity, authority, evidence, policy, and risk
Review basis
Decision Receipt
What Relay returns
Preserves decision, factors, reason, next step, and trace
Response
Why the schema matters
Structured Agent action can support durable review
Attributable
Actor and capability are explicit
Factor-ready
Authority, evidence, policy, and risk are explicit
Versioned
Action stays tied to active versions