{"id":"probe.l6.protocol.v1","title":"Endpoints that speak an agent protocol","unit":"ratio (0–1)","chain_set":"eip155:8453 (Base)","window":"most recent sweep","definition":"Share of the same sample whose registration reached L5 and at least one endpoint completed one of three handshakes: MCP (a POSTed initialize returns a JSON-RPC result with a protocolVersion string, as JSON or as one server-sent-event data line), A2A (an agent card, at the declared card URL or at /.well-known/agent-card.json or agent.json on the endpoint's host, that is a JSON object with a string name and a skills array), or x402 (a 402 whose body, or base64 PAYMENT-REQUIRED header, holds accepts[] with an entry naming a scheme, a network and a payTo address).","method":"The MCP handshake is sent only to endpoints the registration declares as MCP or whose path ends in /mcp or /sse; the A2A card is read only for endpoints declared as A2A or whose URL is a card; the x402 test reads the L5 response and sends nothing extra. Same sandbox as probe.l5.endpoint_live.v2. The first handshake that passes ends the check for that registration.","excludes":["Protocols other than these three.","Endpoints on shared hosting platforms' submit URLs."],"does_not_assert":["That the tools, skills or paid resources do anything useful. A handshake shows the endpoint speaks the protocol, not that its service works or is safe."],"source":"AFG-Pulse liveness probe","since":"2026-10-13","revisions":[],"body_sha256":"68ee6f64cbfe90a7234d3cadd2520f956e10185995b01ea315af254853697df0","url":"https://agenticfinancegraph.com/def/probe.l6.protocol.v1","ladder":"https://agenticfinancegraph.com/ai-agent-liveness-methodology-l0-l9-ladder","license":"https://creativecommons.org/licenses/by/4.0/","attribution":"Agentic Finance Graph — https://agenticfinancegraph.com"}