FlexSim MCP Server

Instructions

Args:
    model_path: Path to .fsm or .fsx file

Example:
    model_path="C:/Models/warehouse.fsm"

Implementation Reference

• mcp_server/flexsim_mcp.py:223-243 (handler)

  Main handler function for flexsim_open_model tool. Uses @mcp.tool() decorator, gets FlexSim controller, opens the model file asynchronously, and returns formatted result with model name and time.

  @mcp.tool()
  async def flexsim_open_model(params: OpenModelInput) -> str:
      """Open a FlexSim model file.
  
      Args:
          model_path: Path to .fsm or .fsx file
  
      Example:
          model_path="C:/Models/warehouse.fsm"
      """
      try:
          controller = await get_controller()
          loop = asyncio.get_event_loop()
          await loop.run_in_executor(None, controller.open, params.model_path)
  
          model_name = Path(params.model_path).stem
          time = controller.time()
  
          return f"✓ Opened: {model_name}\nTime: {format_time(time)}"
      except Exception as e:
          return format_error(e)

• mcp_server/flexsim_mcp.py:67-79 (schema)

  Input validation schema for flexsim_open_model. Uses Pydantic BaseModel to validate model_path is a non-empty string with .fsm or .fsx extension and that the file exists.

  class OpenModelInput(BaseModel):
      """Input for opening a model."""
      model_path: str = Field(..., min_length=1)
  
      @field_validator("model_path")
      @classmethod
      def validate_path(cls, v: str) -> str:
          path = Path(v)
          if path.suffix.lower() not in [".fsm", ".fsx"]:
              raise ValueError("Model must be .fsm or .fsx file")
          if not path.exists():
              raise ValueError(f"File not found: {v}")
          return str(path.resolve())

• mcp_server/flexsim_mcp.py:216-217 (registration)

  FastMCP server instance creation where tools are registered. The flexsim_open_model handler is registered via @mcp.tool() decorator on line 223.

  mcp = FastMCP("flexsim_mcp", lifespan=lifespan)

• mcp_server/flexsim_mcp.py:147-154 (helper)

  Controller management helper that lazily initializes FlexSim controller on first use, ensuring singleton pattern with async lock protection.

  async def get_controller():
      """Get or create the FlexSim controller instance."""
      global _controller
  
      async with _controller_lock:
          if _controller is None:
              _controller = await launch_flexsim()
          return _controller

• mcp_server/flexsim_mcp.py:119-140 (helper)

  Utility functions used by flexsim_open_model: format_time() converts seconds to human-readable format, format_error() creates user-friendly error messages from exceptions.

  def format_time(seconds: float) -> str:
      """Format simulation time as human-readable string."""
      if seconds < 60:
          return f"{seconds:.2f}s"
      elif seconds < 3600:
          return f"{seconds/60:.2f}m"
      else:
          return f"{seconds/3600:.2f}h"
  
  
  def format_error(e: Exception) -> str:
      """Format exception as user-friendly error message."""
      msg = str(e)
      if "not found" in msg.lower():
          return f"Not found: {msg}"
      elif "syntax" in msg.lower():
          return f"FlexScript syntax error: {msg}"
      elif "license" in msg.lower():
          return f"License error: {msg}"
      elif "permission" in msg.lower():
          return f"Permission denied: {msg}"
      return f"Error: {msg}"