MCP Filesystem Server

Instructions

Args:
    ctx: MCP context

Returns:
    List of allowed directories

Implementation Reference

• mcp_filesystem/server.py:283-295 (handler)

  The handler function decorated with @mcp.tool(), which implements the tool logic by retrieving allowed directories from shared components and formatting them for output. This also serves as the registration point.

  @mcp.tool()
  async def list_allowed_directories(ctx: Context) -> str:
      """Returns the list of directories that this server is allowed to access.
  
      Args:
          ctx: MCP context
  
      Returns:
          List of allowed directories
      """
      components = get_components()
      allowed_dirs = components["allowed_dirs"]
      return f"Allowed directories:\n{os.linesep.join(allowed_dirs)}"

• mcp_filesystem/server.py:48-83 (helper)

  Helper function that initializes and caches shared components, including the 'allowed_dirs' list used by the tool handler.

  def get_components() -> Dict[str, Any]:
      """Initialize and return shared components.
  
      Returns cached components if already initialized.
  
      Returns:
          Dictionary with initialized components
      """
      # Return cached components if available
      if _components_cache:
          return _components_cache
  
      # Initialize components
      allowed_dirs_typed: List[Union[str, Path]] = get_allowed_dirs()
      validator = PathValidator(allowed_dirs_typed)
      operations = FileOperations(validator)
      advanced = AdvancedFileOperations(validator, operations)
      grep = GrepTools(validator)
  
      # Store in cache
      _components = {
          "validator": validator,
          "operations": operations,
          "advanced": advanced,
          "grep": grep,
          "allowed_dirs": validator.get_allowed_dirs(),
      }
  
      # Update cache
      _components_cache.update(_components)
  
      logger.info(
          f"Initialized filesystem components with allowed directories: {validator.get_allowed_dirs()}"
      )
  
      return _components