MCP Lottery Demo

Instructions

Implementation Reference

• src/server.js:139-177 (handler)

  Main handler for draw_lottery tool execution within the CallToolRequestSchema handler. Performs input validation, random selection (with optional duplicates), and returns formatted text response.

  case 'draw_lottery': {
    // 抽签工具：从选项列表中随机抽取结果
    const { options, count = 1, allow_duplicate = false } = args;
    
    // 参数验证
    if (!Array.isArray(options) || options.length === 0) {
      throw new Error('选项列表不能为空');
    }
    
    if (count > options.length && !allow_duplicate) {
      throw new Error('抽取数量不能超过选项数量（不允许重复时）');
    }
  
    // 执行抽签逻辑
    const results = [];
    const availableOptions = [...options];  // 创建选项副本
  
    for (let i = 0; i < count; i++) {
      // 随机选择索引
      const randomIndex = Math.floor(Math.random() * availableOptions.length);
      const selected = availableOptions[randomIndex];
      results.push(selected);
      
      // 如果不允许重复，从可用选项中移除已选择的
      if (!allow_duplicate) {
        availableOptions.splice(randomIndex, 1);
      }
    }
  
    // 返回格式化的结果
    return {
      content: [
        {
          type: 'text',
          text: `🎲 抽签结果：\n${results.map((result, index) => `${index + 1}. ${result}`).join('\n')}`,
        },
      ],
    };
  }

• src/server.js:53-77 (schema)

  JSON Schema definition for the draw_lottery tool input parameters: options (required array of strings), count (number, default 1), allow_duplicate (boolean, default false).

  {
    name: 'draw_lottery',
    description: '从给定的选项列表中随机抽取一个或多个结果',
    inputSchema: {
      type: 'object',
      properties: {
        options: {
          type: 'array',
          items: { type: 'string' },
          description: '抽签选项列表',
        },
        count: {
          type: 'number',
          description: '抽取数量，默认为1',
          default: 1,
        },
        allow_duplicate: {
          type: 'boolean',
          description: '是否允许重复抽取，默认为false',
          default: false,
        },
      },
      required: ['options'],  // 必需参数
    },
  },

• src/server.js:118-122 (registration)

  Registration of the tools list (including draw_lottery) via setRequestHandler for ListToolsRequestSchema.

  server.setRequestHandler(ListToolsRequestSchema, async () => {
    return {
      tools,  // 返回工具列表
    };
  });

• src/server-http.js:75-107 (handler)

  HTTP server handler for draw_lottery within handleToolCall function. Identical logic to stdio version.

  case 'draw_lottery': {
    const { options, count = 1, allow_duplicate = false } = args;
    
    if (!Array.isArray(options) || options.length === 0) {
      throw new Error('选项列表不能为空');
    }
    
    if (count > options.length && !allow_duplicate) {
      throw new Error('抽取数量不能超过选项数量（不允许重复时）');
    }
  
    const results = [];
    const availableOptions = [...options];
  
    for (let i = 0; i < count; i++) {
      const randomIndex = Math.floor(Math.random() * availableOptions.length);
      const selected = availableOptions[randomIndex];
      results.push(selected);
      
      if (!allow_duplicate) {
        availableOptions.splice(randomIndex, 1);
      }
    }
  
    return {
      content: [
        {
          type: 'text',
          text: `🎲 抽签结果：\n${results.map((result, index) => `${index + 1}. ${result}`).join('\n')}`,
        },
      ],
    };
  }

• src/server-http.js:10-34 (schema)

  JSON Schema definition for draw_lottery in HTTP server version.

  {
    name: 'draw_lottery',
    description: '从给定的选项列表中随机抽取一个或多个结果',
    inputSchema: {
      type: 'object',
      properties: {
        options: {
          type: 'array',
          items: { type: 'string' },
          description: '抽签选项列表',
        },
        count: {
          type: 'number',
          description: '抽取数量，默认为1',
          default: 1,
        },
        allow_duplicate: {
          type: 'boolean',
          description: '是否允许重复抽取，默认为false',
          default: false,
        },
      },
      required: ['options'],
    },
  },