MCP Policy Gatekeeper

Instructions

Implementation Reference

• server.py:192-199 (handler)

  The handler logic for the 'delete_file' tool within the call_tool function. It resolves the provided path, checks if the file exists, deletes it using path.unlink() if it does, and returns an appropriate success or error message.

  elif name == "delete_file":
      path = resolve_path(arguments["path"])
      
      if not path.exists():
          return [TextContent(type="text", text=f"Error: File '{arguments['path']}' not found")]
      
      path.unlink()
      return [TextContent(type="text", text=f"✓ File deleted: {arguments['path']}")]

• server.py:112-122 (registration)

  Registration of the 'delete_file' tool in the list_tools() function, including name, description, and input schema.

  Tool(
      name="delete_file",
      description="Delete a file",
      inputSchema={
          "type": "object",
          "properties": {
              "path": {"type": "string", "description": "File path"}
          },
          "required": ["path"]
      }
  ),

• server.py:115-121 (schema)

  Input schema definition for the 'delete_file' tool, specifying the required 'path' parameter.

  inputSchema={
      "type": "object",
      "properties": {
          "path": {"type": "string", "description": "File path"}
      },
      "required": ["path"]
  }

• server.py:135-139 (helper)

  Helper function used by the delete_file handler (and others) to resolve relative paths to absolute paths within the protected directory, enforcing security.

  def resolve_path(relative_path: str) -> Path:
      full_path = (PROTECTED_DIR / relative_path).resolve()
      if not str(full_path).startswith(str(PROTECTED_DIR)):
          raise ValueError("Access denied: Path outside protected directory")
      return full_path