FlexSim MCP Server

Instructions

Args:
    node_path: Path to node
    value: New value to set

Example:
    node_path="Model/Processor1/variables/processtime"
    value=5.0

Implementation Reference

• mcp_server/flexsim_mcp.py:403-435 (handler)

  The main handler function for flexsim_set_node_value. Takes NodeAccessInput with node_path and value, builds FlexScript setvalue command, executes it via controller, and verifies the new value.

  @mcp.tool()
  async def flexsim_set_node_value(params: NodeAccessInput) -> str:
      """Set value in FlexSim tree node.
  
      Args:
          node_path: Path to node
          value: New value to set
  
      Example:
          node_path="Model/Processor1/variables/processtime"
          value=5.0
      """
      try:
          controller = await get_controller()
  
          if params.value is None:
              return "Error: No value provided"
  
          # Build script to set value
          if isinstance(params.value, str):
              script = f'setvalue(node("{params.node_path}"), "{params.value}")'
          else:
              script = f'setvalue(node("{params.node_path}"), {params.value})'
  
          controller.evaluate(script)
  
          # Verify
          verify = f'getvalue(node("{params.node_path}"))'
          new_value = controller.evaluate(verify)
  
          return f"✓ {params.node_path} = {new_value}"
      except Exception as e:
          return format_error(e)

• mcp_server/flexsim_mcp.py:93-96 (schema)

  Input schema definition for node access operations. Defines node_path (required string) and value (optional Any) fields using Pydantic BaseModel.

  class NodeAccessInput(BaseModel):
      """Input for node operations."""
      node_path: str = Field(..., min_length=1)
      value: Any | None = Field(default=None)

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

  FastMCP server instance creation where tools are registered via the @mcp.tool() decorator.

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

• mcp_server/flexsim_mcp.py:129-140 (helper)

  Error formatting utility used by the handler to format exceptions into user-friendly error messages with specific handling for common FlexSim error types.

  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}"

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

  Controller getter function used by the handler to obtain the FlexSim controller instance, launching FlexSim if not already running.

  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