FreeCAD MCP

Instructions

Args:
    code: The Python code to execute.

Returns:
    A message indicating the success or failure of the code execution, the output of the code execution, and a screenshot of the object.

Implementation Reference

• src/freecad_mcp/server.py:406-436 (handler)

  MCP tool handler for 'execute_code': proxies code execution to FreeCADConnection RPC, handles success/error responses, and conditionally adds a screenshot.

  @mcp.tool()
  def execute_code(ctx: Context, code: str) -> list[TextContent | ImageContent]:
      """Execute arbitrary Python code in FreeCAD.
  
      Args:
          code: The Python code to execute.
  
      Returns:
          A message indicating the success or failure of the code execution, the output of the code execution, and a screenshot of the object.
      """
      freecad = get_freecad_connection()
      try:
          res = freecad.execute_code(code)
          screenshot = freecad.get_active_screenshot()
          
          if res["success"]:
              response = [
                  TextContent(type="text", text=f"Code executed successfully: {res['message']}"),
              ]
              return add_screenshot_if_available(response, screenshot)
          else:
              response = [
                  TextContent(type="text", text=f"Failed to execute code: {res['error']}"),
              ]
              return add_screenshot_if_available(response, screenshot)
      except Exception as e:
          logger.error(f"Failed to execute code: {str(e)}")
          return [
              TextContent(type="text", text=f"Failed to execute code: {str(e)}")
          ]

• src/freecad_mcp/server.py:42-44 (helper)

  Helper method in FreeCADConnection class that proxies the execute_code call to the XML-RPC server.

  def execute_code(self, code: str) -> dict[str, Any]:
      return self.server.execute_code(code)

• addon/FreeCADMCP/rpc_server/rpc_server.py:172-195 (helper)

  RPC server implementation in FreeCAD addon: executes the provided Python code using exec() in a queued GUI task, captures stdout, and returns success/error with output.

  def execute_code(self, code: str) -> dict[str, Any]:
      output_buffer = io.StringIO()
      def task():
          try:
              with contextlib.redirect_stdout(output_buffer):
                  exec(code, globals())
              FreeCAD.Console.PrintMessage("Python code executed successfully.\n")
              return True
          except Exception as e:
              FreeCAD.Console.PrintError(
                  f"Error executing Python code: {e}\n"
              )
              return f"Error executing Python code: {e}\n"
  
      rpc_request_queue.put(task)
      res = rpc_response_queue.get()
      if res is True:
          return {
              "success": True,
              "message": "Python code execution scheduled. \nOutput: " + output_buffer.getvalue()
          }
      else:
          return {"success": False, "error": res}