fact

Fact, not memory. Up-to-date library documentation for AI agents, over MCP.

Your AI guesses. fact makes it check.

How do I create a native window in mygo? use fact

fact fetches the current official documentation for the library you ask about, at the version that exists right now, and returns the passages that answer the question.

Why

An assistant answers library questions from what it read during training. That is months old, and it shows:

• APIs that were renamed or removed

• Examples written for a version you are not using

• Methods that never existed

A central documentation index fixes some of this, but it lags too: it has to crawl, and it is always behind the release. fact has no index. It reads the library's own documentation API at the moment you ask.

Related MCP server: RTFD (Read The F*****g Docs)

Install

npm install -g @sankpia/fact-mcp

Requires Node.js 20 or newer. Nothing else — the server is a single file with no runtime dependencies.

Connect

Add to your MCP client's configuration:

{
  "mcpServers": {
    "fact": {
      "type": "stdio",
      "command": "fact-mcp",
      "args": []
    }
  }
}

That is the whole setup. It works with Factory, Claude Code, Cursor, VS Code and any other MCP host.

Claude Code

claude mcp add fact fact-mcp

Cursor / VS Code

Use the JSON above in the client's MCP settings file.

Tools

search

Ask a question about a library. Returns the passages that answer it.

Leave query out and pass only library to get a version list and package overview instead of documentation.

get

Fetch one page or one declaration at full fidelity. Use it once search has told you what to look at.

How names resolve

You can name a library the way you would say it:

When two libraries share a name and neither clearly wins, fact returns the candidates with star counts instead of picking one. Ask again with the module path to disambiguate.

Optional: run a proxy

Direct mode is fine when your network reaches pkg.go.dev quickly. On a slow or lossy route, one query means several round trips and the delay adds up.

A fact-proxy sits next to pkg.go.dev, performs every upstream fetch itself, and returns the material in one response. Set two variables and the client uses it:

export FACT_PROXY_URL=https://your-proxy.example.com
export FACT_PROXY_TOKEN=your-token

To run one, see server/ and scripts/setup-server.sh. The proxy is stateless: no cache, no database, no files.

Configuration

A GITHUB_TOKEN is optional and only affects bare-name lookups. A fine-grained token with no permissions at all is enough, because repository search on public repositories requires none.

Design notes

No index, nothing on disk. Answers come from the source at request time. The only cache is in process memory, expires after five minutes, and dies with the process.

One tool call, not three. Resolving a library is part of search, not a separate step you have to chain.

Markdown, not HTML. pkg.go.dev returns Markdown directly, so the response is what an agent reads best.

Failures are explicit. A miss, an ambiguous name and a rate limit each produce a different message with a next step. None of them is silently answered from stale data.

Development

bun install
bun run typecheck
bun run test-matrix          # 31 cases, every tool argument
bun run inspect              # MCP Inspector

See CONTRIBUTING.md for the full workflow.

License

MIT