quijutsu-mcp

A read-only Model Context Protocol server for QuiJutsu, an anime trivia PvP game. It lets any MCP client (Claude Desktop, Claude Code, Cursor, and others) browse QuiJutsu's Community Asset Library, see the trust record behind each entry, and read player, tournament and contributor leaderboards.

It needs no account and no credentials. It talks to the live game through the same publishable key the website ships to every browser, and that key can only reach a small, deliberately public API.

Quickstart

npx -y quijutsu-mcp

Claude Desktop (claude_desktop_config.json) or Claude Code (.mcp.json):

{
  "mcpServers": {
    "quijutsu": {
      "command": "npx",
      "args": ["-y", "quijutsu-mcp"]
    }
  }
}

Or with the Claude Code CLI:

claude mcp add quijutsu -- npx -y quijutsu-mcp

Streamable HTTP is also built in:

PORT=3000 npx -y -p quijutsu-mcp quijutsu-mcp-http   # MCP endpoint: http://localhost:3000/mcp

Related MCP server: @pocket-agent/mcp-server

Tools

All six are read-only (readOnlyHint: true, destructiveHint: false, idempotentHint: true, openWorldHint: false) and return structuredContent alongside a JSON text block.

Spirit Level is how deep a fan needs to be to know something: 1 is common knowledge, 8 is deep lore. It starts as a reviewer estimate and is taken over by the community vote; a level is certified once it crosses the vote threshold.

Example

You: Is QuiJutsu's entry for Lelouch trustworthy, and who decided how hard it is?

The model calls get_asset_provenance with {"name": "Lelouch"}:

{
  "asset": { "asset_type": "character", "name": "Lelouch Lamperouge", "anime_title": "Code Geass" },
  "provenance": {
    "origin": "community",
    "review_status": "passed",
    "evidence_tier": "major",
    "question_eligible": true
  },
  "spirit_level": {
    "spirit_level": 5,
    "spirit_level_source": "community",
    "spirit_level_community_score": 5,
    "spirit_level_vote_count": 5,
    "spirit_level_certified": false,
    "public_poll": {
      "total_votes": 2,
      "tally": [{ "level": 2, "votes": 1 }, { "level": 5, "votes": 1 }],
      "threshold": 10000,
      "certified": false
    }
  }
}

So: a player proposed it, independent reviewers confirmed it against a major source, the game may build questions on it, and its level 5 rating comes from community votes but is not yet certified.

How access is limited

MCP client ──stdio/HTTP──▶ quijutsu-mcp ──publishable key──▶ PostgREST /rpc/<fn>
                                                               │
                                     SECURITY DEFINER functions granted to anon
                                                               │
                                     tables: RLS on, no anon policy, no anon grant

• Every underlying table has row-level security with no anonymous policy. Querying a table directly with this key returns a permission error.

• The public surface is a short list of SECURITY DEFINER Postgres functions with EXECUTE granted to anon. This server calls only those, through src/client.ts.

• Rows are projected to an allow-list of fields (pick() in src/client.ts), not stripped. If a function later gains a column such as a user id, it does not reach the client.

• The server refuses to start if given a secret or service-role key.

• Trivia questions, options and answers are the game itself and are never exposed.

• npm run smoke calls every tool against the live API and fails if a response contains a user id, email, question field or per-viewer field.

Configuration

Nothing is required. To point at a different QuiJutsu-compatible backend, set:

The private sibling

QuiJutsu also runs a private MCP server, quijutsu-question-composer, that lets authorised admins compose trivia questions with an AI client. It is the harder problem: OAuth 2.1 against Supabase Auth with JWKS-verified tokens, time-limited leases on blueprint targets so two composers never write the same question, idempotency keys on every write so retries are safe, and a multi-stage server-side evaluation pipeline before anything reaches human review. This public server shares its conventions (Zod schemas with bounds and descriptions, tool annotations, a uniform isError envelope) without any of its write access.

Development

npm install     # also builds via prepare
npm run smoke   # live end-to-end test over stdio

License

Code: MIT. Community Asset Library data is published under the Open Database License (ODbL) 1.0; attribute it to QuiJutsu (quijutsu.com) when you reuse it.