{"title":"The evidence agent — an A2A specialist another agent hands work to","version":"1.1.0","card":"https://scvd.store/.well-known/agent-card.json","protocol_version":"0.3","negotiation":"Send A2A-Version: 1.0 on card and RPC requests for v1. Absent or empty header selects legacy 0.3; patch numbers are ignored. Dialects share task IDs and immutable evidence.","summary":"POST JSON-RPC 2.0 here: method message/send, one data part carrying { task, ...input }. Three read-only tasks, each answered with one bounded artifact: what was observed, when, what the result means and against what, what it does not establish, and where to reproduce it. Free, no account, no conversation, nothing paid.","tasks":{"preflight_endpoint":{"input":{"url":"REQUIRED. The https x402 door a buyer would GET."},"reproduces":"https://scvd.store/api/preflight/v3"},"verify_receipt":{"input":{"receipt":"REQUIRED. The compact JWS.","public_key_hex":"OPTIONAL. Check offline against this key; else the issuer's did:web is resolved.","kind":"OPTIONAL. \"receipt\" (default) or \"offer\"."},"reproduces":"https://scvd.store/api/conformance/v1"},"get_endpoint_readiness":{"input":{"host":"REQUIRED. A hostname, or a URL whose host is read."},"reproduces":"https://scvd.store/corpus/host/{host}.json"}},"example":{"jsonrpc":"2.0","id":1,"method":"message/send","params":{"message":{"kind":"message","role":"user","messageId":"m-1","parts":[{"kind":"data","data":{"task":"preflight_endpoint","url":"https://example.com/api/paid-answer"}}]}}},"what_it_cannot_tell_you":["Whether to pay, or which door to use. The reader draws that line; this agent does not.","Whether a merchant can be trusted. It returns evidence about bytes, a probe and a chain, never a judgment about a person or a company.","Anything a free read cannot: settlement and delivery are paid instruments on the shelf, sold as x402 doors, not as tasks here."],"state":"Completed and failed task results can be retrieved with tasks/get for 86400 seconds. The task ID grants access to its result; keep it private. Request messages and history are not retained. Terminal tasks cannot be canceled or restarted. Expired IDs return task not found.","limits":{"request_bytes":65536,"retained_task_bytes":1048576,"retention_seconds":86400},"methods":["message/send","tasks/get","tasks/cancel"],"unsupported":["Streaming","Push notifications","Asynchronous returnImmediately","Task enumeration","Tenant routing","Extended agent cards"],"never_a_ranking":"Never a ranking, and never a verdict without its derivation and denominator beside it."}