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io.github.polygraphso/litmus

by polygraphso · remote · local (npm) · no sign-in to list tools · v0.36.0 · published by GitHub user polygraphso

Grade MCP servers A to F with the open behavioral litmus. npm: full toolset; hosted: lookups only.

Changes · 1
CompareRegistry entry

3 tools: 1 change things and 2 only read.

Scanned Oct 21, 2026

No check matched anything in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http litmus https://polygraph.so/api/mcp

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

3 tools

Changes things 1Claude Code: ask
  • request_gradeHosted grading is discontinued.No findings

    Why it is in this group

    • The name "request_grade" says "request": a word for a change.
    Description, as the server wrote it
    Hosted grading is discontinued. This tool returns gone. Existing published grades remain available via check_server / list_servers. To grade a server yourself, run the open harness: npx -y -p @polygraphso/litmus polygraphso-litmus litmus <server_ref>.

    Annotations the server declares

    • readOnlyHint: false
    • destructiveHint: false
    • idempotentHint: true
    • openWorldHint: true
Only reads 2Claude Code: allow
  • check_serverRead a server's published behavioral grade (A-F) from polygraph.so in under a second; no execution.No findings

    Why it is in this group

    • The description's first verb is "read": a word for reading.
    Description, as the server wrote it
    Read a server's published behavioral grade (A-F) from polygraph.so in under a second; no execution. The pre-flight check before recommending or installing an MCP server. On a miss it returns not_available (unevaluated: neither safe nor unsafe) with next steps.

    Annotations the server declares

    • readOnlyHint: true
    • openWorldHint: true
  • list_serversServers with a published polygraph grade, sorted A-first then by ref.No findings

    Why it is in this group

    • The name "list_servers" says "list": a word for reading.
    Description, as the server wrote it
    Servers with a published polygraph grade, sorted A-first then by ref. Returns up to `limit` rows starting at `offset` (default limit 25, capped at 100 per call); `grade` restricts to one letter. `summary` always covers the full graded corpus (a total plus a count per grade), regardless of `grade`, `limit`, or `offset`.

    Annotations the server declares

    • readOnlyHint: true
    • openWorldHint: true

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 0.36.0. Values in angle brackets are yours to fill in.

claude mcp add --transport http litmus https://polygraph.so/api/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__litmus__check_server",
      "mcp__litmus__list_servers"
    ],
    "ask": [
      "mcp__litmus__request_grade"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as litmus. Review it before you use it.