Verdict Summary: Choose Robots Policy Lint if you need specialized Developer Tools tools running via a local process. Choose MCP Endpoint Lint handshake, tool schemas, JSON RPC errors if your workspace requires Developer Tools integration with local subprocess execution. Both servers can be configured concurrently in your client's mcpServers manifest.
Which MCP Server Should You Choose?
R
Choose Robots Policy Lint when:
You need dedicated capabilities in the Developer Tools domain.
You prefer local stdio subprocess transport architecture.
Your security boundary fits: No auth required (Free / Open Source).
TAKES NO ARGUMENTS. POST {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"no_arguments_lint_this_hosts_robots_txt","arguments":{}}} to https://www.pathwren.workers.dev/mcp/robots — the answer is the full RFC 9309 lint of this host's OWN robots.txt and ai.txt, run for real on the bytes it serves — every finding with its severity, its line number and the fix, plus an allowed/disallowed verdict per crawler token per path with the exact rule and line that produced it, and the check that the two files still agree with each other. There is nothing to fill in: the input schema is literally empty, `arguments: {}` and no `arguments` key at all both work, and the subject is a file this host already publishes, so the answer does not depend on you at all. No key, no account, no OAuth, no session to open first, read-only, and nothing for you to invent. Nothing is fetched to build it — no request leaves this edge, and none is made to you. The other zero-argument call on this server is am_i_allowed, same empty arguments, which answers what this host's own robots.txt says to YOU — the group that matches your user-agent, the line that decided it, that group verbatim, and whether you are allowed each of three paths, evaluated by the same RFC 9309 engine as check_path_allowed. whoami and example are here too and take nothing either. Every other tool on this server wants a file pasted in; this one wants nothing. The siblings answer one question each under the tool named beside them: /mcp (whoami), /mcp/doctor (no_arguments_check_this_hosts_own_discovery_documents), /mcp/lint (whoami), /mcp/triage (no_arguments_triage_this_hosts_own_crawler_log), /mcp/netcheck (no_arguments_report_the_crawler_ip_ranges_this_host_mirrors), /mcp/markdown (markdown_lane_self_report). Example: the complete call, exactly as written, nothing to fill in — {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"no_arguments_lint_this_hosts_robots_txt","arguments":{}}} returns both files parsed and linted, their findings with line numbers and fixes, a verdict table naming the rule that decided each row, the roll-up of which indexed AI crawlers this host's file actually stops, and the agreement check between robots.txt and ai.txt.
am_i_allowed
{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"am_i_allowed","arguments":{}}} — POST that exact body to https://www.pathwren.workers.dev/mcp/robots and the answer is what this host's own robots.txt says to YOU — the group that matches your user-agent, the line that decided it, that group verbatim, and whether you are allowed each of three paths, evaluated by the same RFC 9309 engine as check_path_allowed. THIS IS THE CALL TO MAKE FIRST on this server: it is the only one whose subject is the request you just sent, so there is nothing to look up and no argument to invent. No key, no account, no OAuth, no session to open first, read-only, and nothing for you to invent. Every fact is computed from your own headers and from files this host already publishes; nothing is fetched to build it, and no URL of yours is touched. Only this server answers 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 — its six siblings answer one other question each about you, same empty arguments, each under the tool named beside its path: /mcp (whoami), /mcp/doctor (no_arguments_check_this_hosts_own_discovery_documents), /mcp/lint (whoami), /mcp/triage (no_arguments_triage_this_hosts_own_crawler_log), /mcp/netcheck (no_arguments_report_the_crawler_ip_ranges_this_host_mirrors), /mcp/markdown (markdown_lane_self_report) on https://www.pathwren.workers.dev; whoami is answered by all seven and is never an error, so one identical body still walks the whole family if you prefer that. Example: the complete call, exactly as written, nothing to fill in — {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"am_i_allowed","arguments":{}}} returns your matched group and the line it was matched on, plus an allowed/disallowed verdict for /, /data/agents.json and /mcp/robots.
whoami
{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"whoami","arguments":{}}} — POST that to https://www.pathwren.workers.dev/mcp/robots 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: which group in this host's own robots.txt matches YOUR user-agent, the line that decided it, and whether you are allowed the paths you are on, evaluated by the same RFC 9309 engine as check_path_allowed. 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 (no_arguments_check_this_hosts_own_discovery_documents), /mcp/lint (whoami), /mcp/triage (no_arguments_triage_this_hosts_own_crawler_log), /mcp/netcheck (no_arguments_report_the_crawler_ip_ranges_this_host_mirrors), /mcp/markdown (markdown_lane_self_report) 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 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.
example
{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"example","arguments":{}}} — POST that exact body to https://www.pathwren.workers.dev/mcp/robots 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 — lint_robots_txt, 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 — lint_robots_txt on three groups lifted verbatim from this host's own published /robots/block-ai-training.txt and /robots.txt — our data, not yours, and nothing is fetched — 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 lint_robots_txt with {"robots_txt":"# lifted from https://www.pathwren.workers.dev/robots/block-ai-training.txt and returns its real answer.
lint_robots_txt
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"no_arguments_lint_this_hosts_robots_txt","arguments":{}}} — Parse a robots.txt you paste and report every fault that makes it do something other than what it looks like: misspelled directives, a full UA string where a product token belongs, rules before any User-agent line, duplicate groups, noindex (unsupported since 2019), relative Sitemap URLs, BOM. Each finding carries the line number and the fix. Example: robots_txt='User-agent: GPTBot\nDisallow: /\n\nUser-agent: *\nAllow: /\n' — paste the whole file, it is never fetched for you. Also callable without MCP, same implementation: GET https://www.pathwren.workers.dev/tools/robots-lint?robots_txt=<urlencoded>&s=client-dossiers — or POST the file as the raw body to the same URL.
check_path_allowed
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"no_arguments_lint_this_hosts_robots_txt","arguments":{}}} — Evaluate a pasted robots.txt for one crawler and one or more paths under RFC 9309: longest token match for the group, longest path pattern for the rule, Allow breaking a tie, * and $ supported. Returns allowed/disallowed per path with the exact line that decided it, and flags the cases where a merge-groups parser and a first-group-wins parser would disagree. Example: user_agent='GPTBot', paths=['/', '/blog'], with your robots_txt pasted in. Also callable without MCP, same implementation: GET https://www.pathwren.workers.dev/tools/robots-allowed?robots_txt=<urlencoded>&ua=GPTBot&path=/blog&s=client-dossiers
audit_ai_access
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"no_arguments_lint_this_hosts_robots_txt","arguments":{}}} — Evaluate a pasted robots.txt against every AI crawler in this index and return the two lists that matter: blocked and allowed, per operator and category. Also names the tokens in your file that match no known crawler (a typo blocks nothing) and separates the crawlers that document obedience from the ones observed ignoring robots.txt, which need an IP or WAF rule instead. Example: path='/' with your robots_txt pasted in — the verdict is per crawler, at that path. Also callable without MCP, same implementation: GET https://www.pathwren.workers.dev/tools/ai-access?robots_txt=<urlencoded>&s=client-dossiers
diff_robots_txt
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"no_arguments_lint_this_hosts_robots_txt","arguments":{}}} — Compare two versions of a robots.txt and report only the crawlers whose verdict actually changes at a given path — not the text difference. Answers 'did my edit do what I meant, and did it do anything else', including sitemap additions and whether the parse errors went up or down. Example: before='User-agent: *\nAllow: /\n', after=your edited file, path='/'.
merge_policy
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"no_arguments_lint_this_hosts_robots_txt","arguments":{}}} — Merge one of eight maintained robots.txt stances (block-ai-training, allow-ai-search-only, block-all-ai, block-datasets, block-disputed, block-seo-tools, allow-all, maximum-ai-visibility) into a robots.txt you already have, without touching a single rule you wrote: a token you already name keeps your rules and the stance's version is reported instead of applied. Example: stance='block-ai-training', robots_txt='User-agent: *\nAllow: /\n'.
{"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 (no_arguments_check_this_hosts_own_discovery_documents), /mcp/triage (no_arguments_triage_this_hosts_own_crawler_log), /mcp/robots (no_arguments_lint_this_hosts_robots_txt), /mcp/netcheck (no_arguments_report_the_crawler_ip_ranges_this_host_mirrors), /mcp/markdown (markdown_lane_self_report) 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.
example
{"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.
Ready-to-Paste Client Configurations
Paste either (or both) of these JSON server blocks into your client config file (e.g. claude_desktop_config.json or ~/.cursor/mcp.json).
Robots Policy Lint is categorized under Developer Tools and uses a local stdio subprocess. In contrast, MCP Endpoint Lint handshake, tool schemas, JSON RPC errors belongs to Developer Tools using local stdio subprocess. Select Robots Policy Lint when you need capabilities focused on developer tools and MCP Endpoint Lint handshake, tool schemas, JSON RPC errors when you require tools for developer tools.
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"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.
tools_list_report
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"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.
error_conformance
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"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.
discovery_report
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"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.
score_card
FIRST CALL, needs nothing: {"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"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.