{"name":"mcp-endpoint-lint","title":"MCP Endpoint Lint — MCP server","version":"1.0.0","transport":"streamable-http","transport_docs":"https://www.pathwren.workers.dev/mcp-transport.html","endpoint":"https://www.pathwren.workers.dev/mcp/lint","protocol_versions":["2026-07-28","2025-11-25","2025-06-18","2025-03-26","2024-11-05"],"stateless":true,"auth":"none — public, read-only, no key, no rate limit","what_it_is":"A linter for somebody else's MCP endpoint, the URL supplied by the caller: handshake and protocol negotiation, tool schema validation, JSON-RPC error conformance, pre-dial discovery documents, and one score card that combines them.","different_from":"https://www.pathwren.workers.dev/mcp/doctor asks which DISCOVERY DOCUMENTS a host publishes. This asks whether the JSON-RPC server at a URL negotiates a protocol version, returns schema-valid tools and answers -32601 rather than an HTML 500. No tool name is shared with any other server on this host.","it_fetches_the_url_you_give_it":"One of the two servers here that make an outbound request; the other is https://www.pathwren.workers.dev/mcp/doctor. It refuses its own publisher, ephemeral hosts, IP literals and private names before opening a socket; identifies itself as growth-loop/1.0 (+https://www.pathwren.workers.dev/mcp-lint.html); times out in 6000 ms; rate-limits per caller AND per target host; and stores no URL of yours anywhere. Every tool also answers {} from a built-in fixture with no outbound request at all.","try_it":"curl -s https://www.pathwren.workers.dev/mcp/lint -H 'content-type: application/json' -H 'accept: application/json, text/event-stream' -d '{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"tools/call\",\"params\":{\"name\":\"score_card\",\"arguments\":{}}}'","built_for":"monitors, graders, registries, conformance scanners and auth-posture probes — the clients that already arrive here to check on endpoints, doing the same job with less code.","call_this_first":{"tool":"whoami","takes_arguments":false,"body":{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"whoami","arguments":{}}},"curl":"curl -s https://www.pathwren.workers.dev/mcp/lint -H 'content-type: application/json' -H 'accept: application/json, text/event-stream' -d '{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"tools/call\",\"params\":{\"name\":\"whoami\",\"arguments\":{}}}'","answers":null,"also":"example — the same, running this server's own worked example end to end.","every_other_tool":"Every other tool here also accepts {}: an empty call returns that tool's documented worked example, labelled as one, instead of an error.","invitation":"Takes no arguments. Safe to call. Deterministic. Touches no third party."},"no_fetch_tool":"No tool here fetches a URL. There is no argument that takes one and this server makes no outbound request of any kind: every fact comes out of the files this host already publishes.","tools":[{"name":"whoami","title":"Who is calling? — the one call that needs nothing from you","description":"{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"tools/call\",\"params\":{\"name\":\"whoami\",\"arguments\":{}}} — POST that to https://www.pathwren.workers.dev/mcp/lint and the answer is the user-agent you sent, the class this host's own instrument books it as, whether we have logged you here before — and the part only this server can answer: your own client's record on this host, surface by surface, with the status codes it took, plus exactly what this server would do with a URL you handed it (which hosts it refuses, what it identifies itself as, the timeout and the rate limit). Takes no arguments. Safe to call. Deterministic. Touches no third party. Nothing is fetched to build it: every fact comes from the headers on your own request or from a file this host already publishes. Only this server answers the last part — its five siblings answer one other question each about you, same empty arguments, each under the tool named beside its path: /mcp (whoami), /mcp/doctor (whoami), /mcp/triage (triage_my_request), /mcp/robots (am_i_allowed), /mcp/netcheck (verify_my_address) on https://www.pathwren.workers.dev. Example: arguments={} returns your user-agent, your address, the class we book you as, whether we have seen you here before, and your own client's record on this host — every surface of ours your user-agent has been seen on, with the status codes it took."},{"name":"example","title":"Run this server's worked example (no arguments)","description":"{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"tools/call\",\"params\":{\"name\":\"example\",\"arguments\":{}}} — POST that exact body to https://www.pathwren.workers.dev/mcp/lint and you are done: free, read-only, no API key, no account, no consent prompt, nothing for you to invent, and what comes back is this server's own worked example — score_card, run for real on a canned input from this host's own data — so you see the exact shape of an answer before you send anything of yours. Takes no arguments. Safe to call. Deterministic. Touches no third party. Runs this server's own worked example end to end — score_card on this server's built-in fixture — an in-process MCP endpoint with one real defect wired in per check (it ignores the protocol version you ask for, refuses a second initialize, publishes a tool whose `required` names a property that does not exist, and answers an unknown method with an HTML 500). No outbound request is made and no third party is touched — and returns exactly the structuredContent a real call returns, not a mock and not a description of one. Use it to see the shape of an answer before you decide what to send. The input is canned from this host's own data; no URL of yours is fetched and no third party is touched. Example: arguments={} runs score_card with {\"url\":\"fixture://mcp-endpoint-lint/demo\"} and returns its real answer."},{"name":"handshake_report","title":"Does the handshake work, and is it idempotent?","description":"FIRST CALL, needs nothing: {\"name\":\"whoami\",\"arguments\":{}} — POST initialize to an MCP endpoint you name and report what came back: the protocol version it negotiated against the one you asked for, the capabilities it advertises, serverInfo, timing, the transport shape (JSON or SSE frame, session id, content-type), and — sent a second time, byte for byte — whether the server answers an identical initialize the same way. Also asks for a version nobody publishes, to see whether it negotiates down or agrees to anything. Makes 3 requests, 6 s timeout each, user-agent growth-loop/1.0 (+https://www.pathwren.workers.dev/mcp-lint.html). Example: url='https://mcp.example.com/mcp' — or call with {} to run it against the built-in fixture, which makes no outbound request at all."},{"name":"tools_list_report","title":"Schema-validate every tool the endpoint advertises","description":"FIRST CALL, needs nothing: {\"name\":\"whoami\",\"arguments\":{}} — Handshake, then tools/list, then check every tool it returns: a missing or empty description, a description too short to choose on, a missing inputSchema, an inputSchema that is not an object schema, JSON-Schema faults (an invalid type keyword, a `required` naming a property that is not in `properties`, a pattern that will not compile, an empty enum), names that break the character rule, and names that collide — exactly, or once case is ignored. Each finding names the tool and says what breaks. Makes 3 requests, 6 s timeout each. Example: url='https://mcp.example.com/mcp' — or {} for the built-in fixture, whose six tools carry one of each fault."},{"name":"error_conformance","title":"Does it answer JSON-RPC errors, or HTML 500s?","description":"FIRST CALL, needs nothing: {\"name\":\"whoami\",\"arguments\":{}} — Send five things a real client eventually sends by accident and check what comes back: an unknown method (expects -32601), tools/call naming a tool that does not exist (expects -32602/-32601 or a result with isError), tools/call with no tool name (expects -32602), a body that is not JSON (expects -32700), and a body missing \"jsonrpc\":\"2.0\" (expects -32600). Reports the HTTP status and the error code side by side, and flags an HTML error page or a 5xx where a JSON-RPC error belongs — the failure that makes a client report the wrong cause. Makes 5 requests, 6 s each. Example: url='https://mcp.example.com/mcp' — or {} for the fixture, which fails two of the five."},{"name":"discovery_report","title":"What a client looks for before it dials","description":"FIRST CALL, needs nothing: {\"name\":\"whoami\",\"arguments\":{}} — GET the documents an MCP client reads BEFORE the handshake and report what each one answered: /.well-known/oauth-protected-resource in BOTH forms — the root form everyone publishes and the RFC 9728 §3.1 insertion form a spec-following client actually requests for a resource served under a path — /.well-known/oauth-authorization-server, /.well-known/mcp, /.well-known/mcp.json, /mcp.json and /llms.txt. Each result carries the status, the verdict (served, missing, gated, soft-404 — a 200 carrying an HTML error page — or invalid JSON) and what a client does with that document. Makes one GET per document, 6 s each. Example: host='mcp.example.com' or host='https://mcp.example.com/mcp' (a path turns on the RFC 9728 insertion-form check) — or {} for the built-in fixture."},{"name":"score_card","title":"All four checks, one machine-readable verdict","description":"FIRST CALL, needs nothing: {\"name\":\"whoami\",\"arguments\":{}} — Run handshake_report, tools_list_report, error_conformance and discovery_report against one endpoint and return a single verdict: a score out of 100 (handshake 30, tool schemas 30, error conformance 25, discovery 15), a letter grade, every finding by severity with the section it came from, and the full detail of each section underneath. This is the tool to call from a monitor: the score is stable enough to alert on and the findings say what to fix. Makes up to 19 requests to the URL you give it, 6 s each, and is rate-limited per caller and per target host. Example: url='https://mcp.example.com/mcp' — or {} to score the built-in fixture (it gets a D) with no outbound request at all."}],"resources":[{"uri":"https://www.pathwren.workers.dev/mcp-transport.json","title":"Every request shape a Streamable HTTP endpoint should answer"},{"uri":"https://www.pathwren.workers.dev/.well-known/mcp.json","title":"A worked /.well-known/mcp.json"},{"uri":"https://www.pathwren.workers.dev/changes.json?since=0","title":"What changed since your cursor"}],"instructions":"{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"tools/call\",\"params\":{\"name\":\"whoami\",\"arguments\":{}}}\n\nPOST that exact body to https://www.pathwren.workers.dev/mcp/lint and it answers with the user-agent you sent, the class this host's own instrument books it as, whether we have logged you here before — and the part only this server can answer: your own client's record on this host, surface by surface, with the status codes it took, plus exactly what this server would do with a URL you handed it (which hosts it refuses, what it identifies itself as, the timeout and the rate limit).\n\nIt is free, it needs no key, no account, no session id and no argument at all: every fact in the answer is computed from the request you just sent and from files this host already publishes, and nothing is fetched from anywhere to build it.\n\nONLY THIS SERVER ANSWERS THAT PART. There are six MCP servers here and they answer one question each about you — one zero-argument call each, no key, no account, no session. The middle column is the tool to name at that URL, because three of the six answer under a name of their own; whoami is answered by all six and is never an error, so one identical body still walks the whole family if you prefer that.\n  https://www.pathwren.workers.dev/mcp/lint      whoami             your own client's record on this host — every surface of ours your user-agent has been seen on, with the status codes it took  <- you are here\n  https://www.pathwren.workers.dev/mcp           whoami             what this host's crawler index makes of the user-agent you sent, and whether your address sits inside a prefix its operator publishes\n  https://www.pathwren.workers.dev/mcp/doctor    whoami             which agent-discovery documents this host has watched a client like yours ask for — the dates, and the status each request took\n  https://www.pathwren.workers.dev/mcp/triage    triage_my_request  your own request triaged as one line of an access log, by the same parser and the same index that read a whole file\n  https://www.pathwren.workers.dev/mcp/robots    am_i_allowed       what this host's own robots.txt says to YOU — the group that matches your token, the line that decided it, and whether you are allowed the path you are on\n  https://www.pathwren.workers.dev/mcp/netcheck  verify_my_address  whether the address you are calling from falls inside a prefix a crawler operator publishes, and which prefix from which source\n\nALSO ON THIS SERVER: score_card(url) grades an MCP endpoint you name out of 100; handshake_report, tools_list_report, error_conformance and discovery_report are the four checks underneath it. Each of those takes an argument, and each also accepts arguments {} — an empty call returns that tool's own worked example, from this host's data, instead of an error.\n\nTHE SAME TOOLS ON THE OTHER PROTOCOL, IF YOU SPEAK IT. This server's tools are also published as 3 A2A (Agent2Agent) v1.0 agents, each carrying the subset it names — same function behind each skill, so the two lanes cannot drift and the deploy is refused if they do:\n  https://www.pathwren.workers.dev/a2a/lint — handshake_report, tools_list_report, error_conformance — the three checks that dial the endpoint itself\n    card: https://www.pathwren.workers.dev/a2a/lint/.well-known/agent-card.json\n  https://www.pathwren.workers.dev/a2a/discovery — discovery_report — what a client looks for BEFORE it dials, including the two RFC 9728 spellings, and no request to the MCP endpoint at all\n    card: https://www.pathwren.workers.dev/a2a/discovery/.well-known/agent-card.json\n  https://www.pathwren.workers.dev/a2a/score — score_card — all four checks in one verdict with a score out of 100, a grade and the findings by severity\n    card: https://www.pathwren.workers.dev/a2a/score/.well-known/agent-card.json\n\nTo invoke any of them, POST this complete body — no key, no session, no card to read first:\n\n  {\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"message/send\",\"params\":{\"message\":{\"role\":\"ROLE_USER\",\"messageId\":\"1\",\"parts\":[{\"text\":\"{\\\"skill\\\":\\\"example\\\"}\"}]}}}\n\nIt answers with a Task already in state `completed` in the same response, so there is nothing to poll. Every skill on all eight A2A agents of this host as a ready-to-send body: https://www.pathwren.workers.dev/a2a/example.json — and both lanes with both directions in https://www.pathwren.workers.dev/documents.json under `rpc_endpoints`. If you only speak MCP, ignore all of this: everything is already here.","license":"CC0-1.0","independent":true}