Local Docs MCP Server

A TypeScript-based Model Context Protocol (MCP) server that exposes multiple local documentation folders (namespaces) to AI assistants via tools and resources.

Features

• 🔌 HTTP Transport: Uses Streamable HTTP on POST /mcp (no stdio)
• 📁 Multi-Namespace Support: Organize docs across multiple roots with namespace isolation
• 🔗 Resource Access: Dynamic resource template docs://{namespace}/{path} for file access
• 🛠️ Three Tools:
  • list_files - List files matching glob patterns across namespaces
  • read_file - Read specific file contents from a namespace
  • search - Search for text across multiple files and namespaces
• 🔒 Security: Path traversal prevention, symlink escape detection, binary file filtering, configurable file size limits
• 📝 MIME Types: Automatic MIME type detection for all files
• ⚙️ Flexible Configuration: Configure via environment variables or docs.config.json

Installation

Dependencies are already installed. If you need to reinstall:

npm install

Configuration

Method 1: Configuration File (docs.config.json)

Create a docs.config.json file in the project root:

{
  "roots": [
    {
      "ns": "docs",
      "path": "./docs"
    },
    {
      "ns": "api",
      "path": "./api-docs"
    },
    {
      "ns": "guides",
      "path": "C:/absolute/path/to/guides"
    }
  ],
  "maxFileKB": 256,
  "allowSymlinks": false,
  "ignore": [
    "**/node_modules/**",
    "**/.git/**",
    "**/dist/**",
    "**/build/**"
  ]
}

Method 2: Environment Variables

Set the DOCS_DIRS environment variable with comma-separated namespace:path pairs:

# Windows PowerShell
$env:DOCS_DIRS="docs:./docs,api:./api-docs,guides:C:/path/to/guides"
npm run dev

Note: Environment variables take precedence and will override/merge with docs.config.json.

Configuration Options

• roots: Array of namespace definitions
  • ns: Namespace identifier (alphanumeric, hyphens, underscores)
  • path: Absolute or relative path to the root directory
• maxFileKB: Maximum file size in kilobytes (default: 256)
• allowSymlinks: Allow symlinks that point outside the namespace (default: false)
• ignore: Glob patterns to ignore (default: node_modules, .git, etc.)
• PORT: Server port via environment variable (default: 3000)

Running the Server

Development Mode (with auto-reload)

npm run dev

Production Mode

npm start

The server will print the MCP URL on startup:

🚀 Local Docs MCP Server running
📁 Registered namespaces:
   - docs: C:\Users\...\mcp-day\docs
   - api: C:\Users\...\mcp-day\api-docs
🔗 MCP URL: http://localhost:3000/mcp
💚 Health check: http://localhost:3000/health

Testing with MCP Inspector

1. Install MCP Inspector (if not already installed):

   npx @modelcontextprotocol/inspector
   

2. Start the server in one terminal:

   npm run dev
   

3. Open MCP Inspector in another terminal:

   npx @modelcontextprotocol/inspector
   

4. Connect to the server:

   • In the Inspector UI, enter the MCP URL: http://localhost:3000/mcp
   • Transport type: HTTP

5. Test the tools:

   List Files (all namespaces):

   {
     "pattern": "**/*.md",
     "max": 50
   }
   

   List Files (specific namespace):

   {
     "pattern": "**/*.md",
     "ns": "docs",
     "max": 50
   }
   

   List Files (multiple namespaces):

   {
     "pattern": "**/*.md",
     "ns": ["docs", "api"],
     "max": 50
   }
   

   Read File:

   {
     "ns": "docs",
     "path": "welcome.md"
   }
   

   Search (all namespaces):

   {
     "query": "MCP",
     "glob": "**/*.md",
     "max": 100
   }
   

   Search (specific namespace):

   {
     "query": "MCP",
     "glob": "**/*.md",
     "ns": "docs",
     "max": 100
   }
   

6. Test Resources:

   • Resources now use namespace URIs: docs://{namespace}/{path}
   • Example: docs://docs/welcome.md, docs://api/endpoints.md
   • Click on any resource link in the Inspector
   • The file content should appear with proper MIME type

Project Structure

mcp-day/
├── server.ts              # Main MCP server implementation
├── src/
│   └── roots.ts          # RootRegistry implementation
├── package.json          # Project configuration
├── tsconfig.json         # TypeScript configuration
├── docs.config.json      # Namespace configuration
├── README.md            # This file
└── docs/                # Default documentation namespace
    ├── welcome.md       # Sample markdown file
    ├── api.md           # API reference
    └── config.json      # Sample JSON file

Tools Reference

list_files

Lists files in the docs directory matching a glob pattern. Can filter by namespace(s).

Input:

• pattern (optional): Glob pattern (default: **/*.{md,mdx,txt,json})
• ns (optional): Namespace(s) to search - string or array. If omitted, searches all namespaces
• max (optional): Maximum results (default: 200)

Output:

• count: Number of files returned
• namespaces: Array of searched namespaces
• files: Array with ns, path, uri, size, mtime, mimeType
• Resource links for each file as docs://{ns}/{path}

read_file

Reads a file from a specific namespace in the docs directory.

Input:

• ns (required): Namespace to read from
• path (required): Relative path to the file within the namespace

Output:

• ns: Namespace
• path: File path
• bytes: File size
• lines: Line count
• Resource link to the file content as docs://{ns}/{path}

search

Searches for text in files. Can filter by namespace(s).

Input:

• query (required): Search text
• glob (optional): File pattern to search
• ns (optional): Namespace(s) to search - string or array. If omitted, searches all namespaces
• max (optional): Maximum matches (default: 100)
• contextLines (optional): Context lines (default: 1)

Output:

• query: Search term
• namespaces: Array of searched namespaces
• matchCount: Number of matches
• matches: Array with ns, path, lineNumber, line, start, end, uri
• Resource links to matched files as docs://{ns}/{path}

Resources

The server exposes dynamic resource templates for each namespace:

• URI Pattern: docs://{namespace}/{path}
• Examples:
  • docs://docs/welcome.md
  • docs://api/endpoints.md
  • docs://guides/tutorial.md
• Returns: File content with correct MIME type

Resources are automatically linked in tool responses and can be opened directly in the MCP Inspector.

Security Features

1. Path Traversal Protection: All paths are validated to ensure they're within the namespace root
2. Symlink Escape Detection: By default, symlinks pointing outside the namespace are blocked (configurable)
3. Binary File Rejection: Binary files are automatically skipped
4. Configurable File Size Limits: Files larger than the configured limit are rejected (default: 256KB)
5. Namespace Validation: Namespace identifiers are validated (alphanumeric, hyphens, underscores only)
6. Ignore Patterns: Automatically skip node_modules, .git, and other configured patterns
7. Sanitized Errors: Error messages don't expose internal paths

Customization

Using Multiple Namespaces

Example 1: Via environment variable

# Windows PowerShell
$env:DOCS_DIRS="docs:./docs,api:./api-docs,guides:C:/guides"
npm run dev

Example 2: Via docs.config.json

{
  "roots": [
    { "ns": "docs", "path": "./docs" },
    { "ns": "api", "path": "./api-docs" },
    { "ns": "guides", "path": "C:/absolute/path/to/guides" }
  ]
}

To add new namespaces, edit the docs.config.json file and restart the server.

Configuring File Size Limits

Edit docs.config.json:

{
  "maxFileKB": 512,
  "roots": [...]
}

Allowing Symlinks

Edit docs.config.json:

{
  "allowSymlinks": true,
  "roots": [...]
}

Warning: Only enable if you trust the symlink targets. This allows symlinks to point outside namespace roots.

Custom Ignore Patterns

Edit docs.config.json:

{
  "ignore": [
    "**/node_modules/**",
    "**/.git/**",
    "**/dist/**",
    "**/build/**",
    "**/*.log",
    "**/tmp/**"
  ],
  "roots": [...]
}

Troubleshooting

Server won't start:

• Check if port 3000 is already in use
• Try a different port: $env:PORT="3001"; npm start
• Check TypeScript compilation errors

Files not appearing:

• Verify namespace configuration in docs.config.json or DOCS_DIRS
• Check that namespace paths exist and are accessible
• Ensure files match the glob pattern
• Check file permissions
• Review ignore patterns

Namespace not found errors:

• Run roots.list tool to see registered namespaces
• Check namespace spelling (case-sensitive)
• Verify docs.config.json is valid JSON
• Check console logs for initialization warnings

Inspector can't connect:

• Verify the server is running
• Check the MCP URL is correct: http://localhost:3000/mcp
• Ensure no firewall is blocking the connection
• Check health endpoint: http://localhost:3000/health

Path traversal or symlink errors:

• Ensure paths are relative to the namespace root
• Check allowSymlinks setting if using symlinks
• Verify symlinks don't escape the namespace directory

File too large errors:

• Increase maxFileKB in docs.config.json
• Or filter out large files using ignore patterns

License

ISC