Filesystem MCP Server

Node.js server implementing Model Context Protocol (MCP) for filesystem operations.

Published on npm as @modelcontextprotocol/server-filesystem.

Features

• Read/write files
• Create/list/delete directories
• Move files/directories
• Search files
• Get file metadata
• Dynamic directory access control via Roots

Directory Access Control

The server uses a flexible directory access control system. Directories can be specified via command-line arguments or dynamically via Roots.

Method 1: Command-line Arguments

Specify Allowed directories when starting the server:

mcp-server-filesystem /path/to/dir1 /path/to/dir2

Method 2: MCP Roots (Recommended)

MCP clients that support Roots can dynamically update the Allowed directories.

Roots notified by Client to Server, completely replace any server-side Allowed directories when provided.

Important: If server starts without command-line arguments AND client doesn't support roots protocol (or provides empty roots), the server will throw an error during initialization.

This is the recommended method, as this enables runtime directory updates via roots/list_changed notifications without server restart, providing a more flexible and modern integration experience.

How It Works

The server's directory access control follows this flow:

1. Server Startup

   • Server starts with directories from command-line arguments (if provided)
   • If no arguments provided, server starts with empty allowed directories

2. Client Connection & Initialization

   • Client connects and sends initialize request with capabilities
   • Server checks if client supports roots protocol (capabilities.roots)

3. Roots Protocol Handling (if client supports roots)

   • On initialization: Server requests roots from client via roots/list
   • Client responds with its configured roots
   • Server replaces ALL allowed directories with client's roots
   • On runtime updates: Client can send notifications/roots/list_changed
   • Server requests updated roots and replaces allowed directories again

4. Fallback Behavior (if client doesn't support roots)

   • Server continues using command-line directories only
   • No dynamic updates possible

5. Access Control

   • All filesystem operations are restricted to allowed directories
   • Use list_allowed_directories tool to see current directories
   • Server requires at least ONE allowed directory to operate

Note: The server will only allow operations within directories specified either via args or via Roots.

API

Tools

• read_text_file

  • Read complete contents of a file as text
  • Inputs:
    • path (string)
    • head (number, optional): First N lines
    • tail (number, optional): Last N lines
  • Always treats the file as UTF-8 text regardless of extension
  • Cannot specify both head and tail simultaneously

• read_media_file

  • Read a file and return it as a base64-encoded content block with its MIME type
  • Inputs:
    • path (string)
  • Streams the file and returns base64 data with the corresponding MIME type. Image and audio files are returned as image/audio content; any other file type is returned as an embedded resource (a valid MCP content block for arbitrary binary data)

• read_multiple_files

  • Read multiple files simultaneously
  • Input: paths (string[])
  • Failed reads won't stop the entire operation

• write_file

  • Create new file or overwrite existing (exercise caution with this)
  • Inputs:
    • path (string): File location
    • content (string): File content

• edit_file

  • Make selective edits using