{
  "schema_version": "a2a_callback_receiver.v1",
  "mode": "receive_a2a_callback",
  "event_type": "receipt.verified",
  "source_agent_id": "external.agent.alpha",
  "production_run_id": "run_001",
  "return_package_id": "return_package_001",
  "receipt_id": "receipt_001",
  "verification_id": "verification_001"
}