MCP Filesystem Server

Instructions

Args:
    path: Path to write to
    content: Content to write
    encoding: File encoding (default: utf-8)
    create_dirs: Whether to create parent directories if they don't exist
    ctx: MCP context

Returns:
    Success or error message

Implementation Reference

• mcp_filesystem/server.py:144-170 (handler)

  MCP tool handler for 'write_file'. This is the entry point decorated with @mcp.tool() that handles the tool call, gets components, and delegates to FileOperations.write_file.

  @mcp.tool()
  async def write_file(
      path: str,
      content: str,
      ctx: Context,
      encoding: str = "utf-8",
      create_dirs: bool = False,
  ) -> str:
      """Create a new file or overwrite an existing file with new content.
  
      Args:
          path: Path to write to
          content: Content to write
          encoding: File encoding (default: utf-8)
          create_dirs: Whether to create parent directories if they don't exist
          ctx: MCP context
  
      Returns:
          Success or error message
      """
      try:
          components = get_components()
          await components["operations"].write_file(path, content, encoding, create_dirs)
          return f"Successfully wrote to {path}"
      except Exception as e:
          return f"Error writing file: {str(e)}"

• mcp_filesystem/operations.py:161-205 (helper)

  Core implementation of file writing logic in the FileOperations class. Validates path security, creates parent directories if specified, and writes content (supports str or bytes).

  async def write_file(
      self,
      path: Union[str, Path],
      content: Union[str, bytes],
      encoding: str = "utf-8",
      create_dirs: bool = False,
  ) -> None:
      """Write to a file.
  
      Args:
          path: Path to the file
          content: Content to write (string or bytes)
          encoding: Text encoding for string content
          create_dirs: Whether to create parent directories if they don't exist
  
      Raises:
          ValueError: If path is outside allowed directories
          PermissionError: If file cannot be written
      """
      abs_path, allowed = await self.validator.validate_path(path)
      if not allowed:
          raise ValueError(f"Path outside allowed directories: {path}")
  
      # Create parent directories if requested
      if create_dirs:
          parent_dir = abs_path.parent
          if not parent_dir.exists():
              try:
                  await anyio.to_thread.run_sync(
                      partial(parent_dir.mkdir, parents=True)
                  )
              except (PermissionError, FileNotFoundError) as e:
                  raise ValueError(f"Cannot create parent directories: {e}")
  
      # Write content
      try:
          if isinstance(content, str):
              await anyio.to_thread.run_sync(
                  partial(abs_path.write_text, content, encoding=encoding)
              )
          else:
              await anyio.to_thread.run_sync(partial(abs_path.write_bytes, content))
      except PermissionError as e:
          raise ValueError(f"Cannot write to file: {e}")