{"transport":"A2A JSON-RPC 2.0","method":"POST /a2a","supported":{"message/send":"A2A 0.3.0","SendMessage":"A2A 1.0.1"},"hint":"POST message/send (A2A 0.3.0) or SendMessage (A2A 1.0.1) with your RFC 9421 signed request in a data part to diagnose it; add skill=verify-rfc9421 + public_key_hex for a verdict. The reply is in the same protocol version you called.","card":"/.well-known/agent-card.json"}