{"uri":"https://agent-guild-5d5r.onrender.com/extensions/machine-envelope/v1","name":"Agent Guild A2A Machine Envelope","version":"1.0","status":"stable","scope":"A2A vendor extension; not part of the core A2A specification","documentation":"/extensions/machine-envelope/v1.md","agent_card":{"location":"capabilities.extensions[]","required":true,"fields":["uri","description","required","params"],"params":{"required":["metadata_key","recipient","kind","context_protocol","acquisition","free_discovery"],"receiver_policy":["recipient","kind","context_protocol"]}},"activation":{"http_header":"A2A-Extensions","http_header_member":"https://agent-guild-5d5r.onrender.com/extensions/machine-envelope/v1","message_field":"extensions[]","message_field_role":"optional descriptive declaration; when present it remains inside the signed semantic Message","required_both":false,"response_echo":"A2A-Extensions"},"message":{"metadata_key_parameter":"params.metadata_key","default_metadata_key":"io.agent-guild/machine-envelope","semantic_payload":"RFC 8785 JCS of the complete A2A Message after removing only the declared envelope metadata entry","bound_fields":"all Message fields including extensions and all other metadata"},"verification":{"before_side_effects":true,"requirements":["pinned issuer and valid signature","exact SHA-256 semantic-payload digest","exact Agent Card recipient and kind","context protocol and A2A messageId","current validity window","durable atomic consume before side effects"],"proof_boundary":"provenance and authorization, not payload truth or policy safety","reference_receiver":"/sdk/integrations/machine_envelope_receiver.mjs","reference_buyer":"/sdk/agentguild_envelope_client.mjs"},"errors":{"machine_envelope_extension_required":"activation absent or incomplete","machine_envelope_required":"activation accepted but envelope absent","machine_envelope_rejected":"signature, binding, policy, validity, or replay failure"},"discovery":{"free":true,"acquisition":"receiver-specific params.acquisition","unsigned_retry_never_authorizes":true}}