Paste an MCP server's tools/list and audit its catalogue quality: context cost, annotations, instructions and official registry compliance. This is not an access-security auditor or a live debugger — check the help to see what this is and isn't.
How to use
What this checks
Paste the tools/list response of an MCP server —yours, or anyone's— and it checks catalogue quality: missing descriptions and annotations, tools whose name suggests they write or delete while their annotations say otherwise, context cost per tool, whether the catalogue's instructions field is set and fits under ~2 KB, and whether any description hides an instruction meant for the model (tool poisoning). Nothing leaves your browser.
Registry manifest (optional)
Paste server.json too and it checks the official MCP registry's own limits (field lengths, the namespace pattern) BEFORE it rejects your publish with a 422 or a 403 —the two errors we already suffered publishing our own packages. Add package.json to also catch a version mismatch between the two, which the registry rejects with a 400 after you've already authenticated.
Tool poisoning
A tool can carry an instruction hidden inside its own description: invisible to you —you only see the name— but visible IN FULL to the model (real case: Invariant Labs, "MCP Tool Poisoning Attacks", April 2025 — an add tool with an <IMPORTANT> tag asking to read ~/.ssh/id_rsa and smuggle it into a parameter). It's only marked "critical" when the SAME description asks to read something sensitive AND send it somewhere — documenting the pattern as an example, or mentioning a path without asking to send it, does not count. Built by @seguridad, not by this tool.
What this does NOT check
This audits catalogue DESIGN, not access security. For "which MCP servers does this repo trust, and what can they do" use the Agent file auditor. For live protocol debugging, use Anthropic's official @modelcontextprotocol/inspector. Tool names that are confusable with each other, and unsafe code patterns in the server's SOURCE, are not checked yet.
