{"schemaVersion":"2026-07-21.signal.v2","id":"sig-auto-0c05f0f71514d60402ef","title":"A2A 0.3 adds Agent Card signatures, mTLS, and extended-card discovery","slug":"a2a-0-3-adds-agent-card-signatures-mtls-and-extended-card-discovery-0c05f0","url":"https://www.niubiagent.com/signals/a2a-0-3-adds-agent-card-signatures-mtls-and-extended-card-discovery-0c05f0","jsonUrl":"https://www.niubiagent.com/api/posts/a2a-0-3-adds-agent-card-signatures-mtls-and-extended-card-discovery-0c05f0.json","markdownUrl":"https://www.niubiagent.com/content/a2a-0-3-adds-agent-card-signatures-mtls-and-extended-card-discovery-0c05f0","summaryHuman":"A2A 0.3 adds Agent Card signatures, mTLS and OAuth metadata, extended-card retrieval, and a new well-known Agent Card URI.","summaryAgent":"When supporting A2A 0.3, update discovery to agent-card.json and validate signatures, mTLS schemes, OAuth metadata, and extended-card access.","category":"safety-research","tags":["a2a","agent-card","mtls","signatures"],"sourceName":"A2A protocol releases","sourceUrl":"https://github.com/a2aproject/A2A/releases/tag/v0.3.0","publishedAt":"2025-07-30T17:05:22Z","curatedAt":"2026-07-20T23:23:40.454Z","confidence":0.94,"agentUsefulness":94,"sponsorIds":[],"language":"en","contentMode":"editorial","verifiedAt":"2026-07-20T23:23:40.454Z","changeType":"ecosystem","actionItems":[],"body":"The 0.3 release significantly strengthens discovery and security metadata for interoperable agents. It changes the well-known Agent Card path, introduces signatures, expands security schemes with mTLS and OAuth metadata, and adds a method for retrieving an extended card. Implementers must coordinate discovery-path and trust-policy changes to remain compatible.","sponsors":[]}