docs-mcp

Fast local MCP server that indexes documentation sites by base URL and serves keyword search, optional semantic search, and Markdown page retrieval as MCP tools — all from a single SQLite file.

• Bun + TypeScript runtime, bun:sqlite + sqlite-vec storage, FTS5 (BM25) full-text + optional vec0 KNN vectors fused via Reciprocal Rank Fusion (with per-page diversity cap).

• Both stdio and Streamable HTTP MCP transports.

• Auto-detects any OpenAI-compatible embeddings endpoint (Ollama, LM Studio, OpenAI, …) — falls back to BM25 if none is reachable.

• Polite crawler: sitemap-first (gzip-aware), BFS fallback on raw HTML (so nav/TOC links count), robots.txt-aware, per-origin QPS, exponential backoff with jitter, conditional GETs.

• Optional playwright fetcher for JS-rendered (SPA) docs sites.

• Async indexing: kick off a crawl and have agents start search_docs immediately while the index fills in the background.

Quick start

1. Install

git clone https://github.com/kage1020/docs-mcp.git
cd docs-mcp
bun install

The entry point is bin/docs-mcp. Reference it by absolute path in your agent config below. (Optional: bun build --compile bin/docs-mcp --outfile dist/docs-mcp to produce a standalone binary.)

2. (Optional) enable semantic search

Any OpenAI-compatible embeddings endpoint works. The simplest is Ollama:

ollama pull embeddinggemma
# or any other embedding model — set DOCS_MCP_EMBEDDING_MODEL to match.

Then add the two env vars below to your agent config. Without these, docs-mcp runs in BM25-only mode (still very useful, just no semantic fallback).

3. Wire into your agent

All configs use the same { command, args, env } shape. Replace /ABSOLUTE/PATH/TO/docs-mcp with where you cloned the repo.

Edit claude_desktop_config.json:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

• Windows: %APPDATA%\Claude\claude_desktop_config.json

• Linux: ~/.config/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "docs": {
      "command": "bun",
      "args": ["run", "/ABSOLUTE/PATH/TO/docs-mcp/bin/docs-mcp", "serve", "--stdio"],
      "env": {
        "DOCS_MCP_EMBEDDING_BASE_URL": "http://localhost:11434/v1",
        "DOCS_MCP_EMBEDDING_MODEL": "embeddinggemma"
      }
    }
  }
}

Restart Claude Desktop. The 7 tools appear under the hammer icon.

Create .mcp.json at the project root:

{
  "mcpServers": {
    "docs": {
      "command": "bun",
      "args": ["run", "/ABSOLUTE/PATH/TO/docs-mcp/bin/docs-mcp", "serve", "--stdio"],
      "env": {
        "DOCS_MCP_EMBEDDING_BASE_URL": "http://localhost:11434/v1",
        "DOCS_MCP_EMBEDDING_MODEL": "embeddinggemma"
      }
    }
  }
}

Claude Code prompts to approve the server on next launch in that project. Or register globally:

claude mcp add docs -- bun run /ABSOLUTE/PATH/TO/docs-mcp/bin/docs-mcp serve --stdio

Create .cursor/mcp.json (project) or ~/.cursor/mcp.json (global):

{
  "mcpServers": {
    "docs": {
      "command": "bun",
      "args": ["run", "/ABSOLUTE/PATH/TO/docs-mcp/bin/docs-mcp", "serve", "--stdio"],
      "env": {
        "DOCS_MCP_EMBEDDING_BASE_URL": "http://localhost:11434/v1",
        "DOCS_MCP_EMBEDDING_MODEL": "embeddinggemma"
      }
    }
  }
}

Most MCP-aware clients accept the same JSON shape; look for a "MCP servers" or "Model Context Protocol" section in settings. If your client only takes a command string, use:

bun run /ABSOLUTE/PATH/TO/docs-mcp/bin/docs-mcp serve --stdio

Start the server once:

DOCS_MCP_EMBEDDING_BASE_URL=http://localhost:11434/v1 \
DOCS_MCP_EMBEDDING_MODEL=embeddinggemma \
bun run /ABSOLUTE/PATH/TO/docs-mcp/bin/docs-mcp serve --http --port 7777

Then point any MCP client (Streamable HTTP transport) at http://127.0.0.1:7777/mcp.

4. First crawl

From any of the agents above, ask it to:

Index https://nextjs.org/docs in the background, then search for "app router".

Internally this calls add_site with wait:false, then search_docs. The agent can poll index_status to see progress.

Related MCP server: Atlas

Develop / contribute

bun install
bun run test
bun run check
bun run typecheck
bun run bench

CLI

docs-mcp --help
docs-mcp --version

# MCP transports
docs-mcp serve --stdio
docs-mcp serve --http --port 7777

# Site management
docs-mcp add <base_url> [--name X]
docs-mcp list
docs-mcp refresh --id <site_id> [--full]
docs-mcp remove --id <site_id>

MCP tools (7)

search_docs

{
  "query": "campaign budget",
  "site_id": 1,             // optional
  "top_k": 10,              // 1..50, default 10
  "mode": "auto",           // "bm25" | "vector" | "hybrid" | "auto"
  "max_per_page": 2         // 1..50, default 2 — cap hits per pageUrl
}

Returns structuredContent.hits shaped like:

{
  chunkId: number;
  pageUrl: string;
  pageTitle: string | null;
  headingPath: string;     // "Guide > Routing > CampaignService"
  snippet: string;         // BM25 highlight (`<<…>>`) or first 200 chars
  description: string;     // First non-code paragraph of the chunk
  codeBlocks: Array<{ language: string | null; code: string }>;
  tables: Array<{ headers: string[]; rows: string[][] }>;
  score: number;           // normalized 0..1
  source: "bm25" | "vector" | "both";
}

The content text mirrors this as a context7-style render — each hit becomes a ### heading / Source: … / description / fenced code / table block, so agents can answer the user without a separate get_doc round-trip when the answer fits in a chunk.

Spec-table docs (Yahoo Ads, OpenAPI-style references) get a two-step boost: (1) the extractor detects field-definition <table>s and restructures each row into <h4>fieldName</h4> + meta + description HTML before turndown, and (2) the chunker splits on h1–h4 so each field lands in its own chunk with `headingPath = "Service > Section

fieldName". BM25 then matches the field name directly, and the chunk's descriptioncarries the per-field doc — noget_doc` needed to enumerate fields.

Unknown site_id returns isError: true instead of silently empty hits. A known but unindexed site_id (e.g. crawl still running) returns structuredContent.siteEmpty: true plus a hint to poll index_status, so agents don't silently treat "no pages yet" as "no matching content".

get_doc

{
  "url": "https://docs.example.com/page",
  "max_chars": 60000,       // 100..500000
  "persist": false          // true -> also insert into pages + chunks
}

• DB cache hit ⇒ source: "cache" (1-2 ms).

• LRU memory-cache hit ⇒ source: "memory-cache" (50 entries / 30 min TTL).

• Cold fetch ⇒ source: "fetched". Honors robots.txt for the target host (cached per origin).

• persist: true requires a registered site whose base_url covers the URL; embeddings are computed if a model is configured.

add_site

{
  "base_url": "https://docs.example.com/",
  "name": "example",
  "include_patterns": ["/api/**"],
  "exclude_patterns": ["/api/legacy/**"],
  "max_depth": 5,
  "max_pages": 2000,
  "wait": true              // false -> return immediately, crawl runs async
}

Idempotent: calling twice with the same base_url returns the existing siteId. Parallel calls fold into a single background crawl. wait: false returns structuredContent.status = "indexing".

If a crawl yields 0 pages, or the base URL turns out to be a JS-rendered shell (no in-scope <a> links in raw HTML), structuredContent.warnings is populated — for example with a hint to set DOCS_MCP_RENDER=playwright.

index_status

{ "site_id": 1 }
// -> { status: "indexing"|"idle", pagesIndexed, chunksIndexed,
//      startedAt, error: string|null, warnings: string[] }

warnings carries the most recent crawl's hints (e.g. "JS-rendered shell detected — try DOCS_MCP_RENDER=playwright") for the lifetime of the server process.

Configuration (env)

When the embedding endpoint is unreachable, the server logs a warning and continues in BM25-only mode. Same when sqlite-vec can't load (older macOS) — search degrades to BM25.

SPA rendering with playwright (optional)

For sites where pages render in the browser (parts of developers.google.com, many SPA docs apps), set DOCS_MCP_RENDER=playwright.

bun add -d playwright
bunx playwright install chromium

Chromium is launched directly from Bun and driven over CDP via a raw WebSocket connection (src/crawler/cdp-client.ts). Playwright is used only to locate the chromium executable — its in-process launcher can't speak chromium's pipe IPC under Bun-on-Windows, and the ws-based connectOverCDP fallback hangs in the same environment. Pin the chromium binary via createPlaywrightFetcher({ executablePath }) if you need a non-default install.

Performance benchmarks

bun run bench
bun run bench:diff bench-baseline.json bench-result.json --threshold 0.2

The CI pipeline runs bench:diff against bench-baseline.json (captured on the GitHub Linux runner) on every push/PR; >20% slowdowns fail the build. Update the baseline by replacing it with a fresh bench-result.json.

Indicative single-thread numbers (Ubuntu CI runner):

License

MIT