Unity AI Bridge

Instructions

Implementation Reference

• .claude/skills/unity-bridge/mcp_server.py:178-225 (handler)

  The tool handler in the MCP server proxies calls to the Unity bridge via file-based IPC. The actual tool implementation is not statically defined in the Python code but is dispatched dynamically to the Unity Editor using the name passed in the `call_tool` function.

  def call_tool(name, arguments):
      """Execute a Unity Bridge tool via file IPC. Returns MCP content result."""
      bridge_dir = get_bridge_dir()
      commands_dir = os.path.join(bridge_dir, "commands")
      results_dir = os.path.join(bridge_dir, "results")
  
      # Heartbeat check
      err = check_heartbeat(bridge_dir)
      if err:
          return True, err
  
      # Write command
      command_id = f"{int(time.time())}-{uuid.uuid4().hex[:8]}"
      command = {"id": command_id, "tool": name, "params": arguments or {}}
  
      os.makedirs(commands_dir, exist_ok=True)
      os.makedirs(results_dir, exist_ok=True)
  
      command_file = os.path.join(commands_dir, f"{command_id}.json")
      write_atomic(command_file, json.dumps(command))
  
      # Poll for result
      result_file = os.path.join(results_dir, f"{command_id}.json")
      elapsed = 0.0
  
      while not os.path.exists(result_file):
          time.sleep(IPC_POLL_INTERVAL)
          elapsed += IPC_POLL_INTERVAL
          if elapsed >= IPC_TIMEOUT:
              try:
                  os.remove(command_file)
              except OSError:
                  pass
              return True, f"Timeout after {IPC_TIMEOUT}s waiting for Unity (tool: {name})"
  
      # Read result
      try:
          with open(result_file, "r", encoding="utf-8") as f:
              result = json.load(f)
      finally:
          try:
              os.remove(result_file)
          except OSError:
              pass
  
      is_error = result.get("status") != "success"
      message = result.get("message", "")
      return is_error, message