MCP GameBoy Server

Instructions

Implementation Reference

• src/tools.ts:28-35 (handler)

  Handler logic for the 'press_left' tool (shared with other press_* tools): presses the LEFT button for the specified duration and returns the current screen image.

  async ({ duration_frames }): Promise<CallToolResult> => {
    // Press the button using the service (advances one frame)
    emulatorService.pressButton(button, duration_frames);
  
    // Return the current screen using the service
    const screen = emulatorService.getScreen();
    return { content: [screen] };
  }

• src/tools.ts:25-27 (schema)

  Input schema for 'press_left' tool: optional duration_frames (number of frames to hold LEFT button, default 25).

  {
    duration_frames: z.number().int().positive().optional().default(1).describe('Number of frames to hold the button').default(25)
  },

• src/tools.ts:20-37 (registration)

  Dynamic registration of 'press_left' tool (for GameBoyButton.LEFT) along with other press_* tools on the MCP server.

  // Register button press tools
  Object.values(GameBoyButton).forEach(button => {
    server.tool(
      `press_${button.toLowerCase()}`,
      `Press the ${button} button on the GameBoy`,
      {
        duration_frames: z.number().int().positive().optional().default(1).describe('Number of frames to hold the button').default(25)
      },
      async ({ duration_frames }): Promise<CallToolResult> => {
        // Press the button using the service (advances one frame)
        emulatorService.pressButton(button, duration_frames);
  
        // Return the current screen using the service
        const screen = emulatorService.getScreen();
        return { content: [screen] };
      }
    );
  });

• src/types.ts:9-18 (helper)

  GameBoyButton enum defining the LEFT button used to register and identify the 'press_left' tool.

  export enum GameBoyButton {
    UP = 'UP',
    DOWN = 'DOWN',
    LEFT = 'LEFT',
    RIGHT = 'RIGHT',
    A = 'A',
    B = 'B',
    START = 'START',
    SELECT = 'SELECT'
  }

• src/emulatorService.ts:72-80 (helper)

  Core pressButton implementation in EmulatorService that handles pressing the LEFT button on the underlying GameBoyEmulator.

  pressButton(button: GameBoyButton, durationFrames: number): ImageContent {
    log.debug(`Pressing button: ${button}`);
    if (!this.isRomLoaded()) {
      log.warn('Attempted to press button with no ROM loaded');
      throw new Error('No ROM loaded');
    }
    this.emulator.pressButton(button, durationFrames); // This advances one frame
    return this.getScreen();
  }