Lemonade Stand MCP Server

Instructions

Implementation Reference

• server.js:303-313 (handler)

  Handler for the 'start_game' tool: generates a unique game ID, creates initial game state using createNewGame(), stores it in the games Map, and returns the gameId and state as JSON.

  case 'start_game': {
    const gameId = uuidv4();
    const initialGameState = createNewGame();
    games.set(gameId, initialGameState);
    return {
      content: [{
        type: "text",
        text: JSON.stringify({ gameId, gameState: initialGameState })
      }]
    };
  }

• server.js:237-244 (registration)

  Registration of the 'start_game' tool in the ListTools response, including its name, description, and empty input schema.

  {
    name: "start_game",
    description: "Start a new lemonade stand game",
    inputSchema: {
      type: "object",
      properties: {}
    }
  },

• server.js:46-59 (helper)

  Helper function createNewGame() that initializes the game state with starting money, empty inventory, initial price, weather, and status.

  const createNewGame = () => ({
    day: 1,
    money: 20.00,
    inventory: {
      cups: 0,
      lemons: 0,
      sugar: 0,
      ice: 0
    },
    purchaseHistory: [],  // Keep track of purchases for proper cost calculation
    pricePerCup: 0.25,
    weather: generateWeather(),
    status: 'buying'
  });

• server.js:38-43 (helper)

  Helper function generateWeather() used by createNewGame to set initial weather conditions.

  const generateWeather = () => {
    const temp = Math.floor(Math.random() * 40) + 50; // 50-90°F
    const conditions = ['Sunny', 'Partly Cloudy', 'Cloudy', 'Rainy'];
    const condition = conditions[Math.floor(Math.random() * conditions.length)];
    return { temp, condition };
  };