MySQL MCP Server

Instructions

Implementation Reference

• src/index.ts:218-264 (handler)

  Main handler function that validates the SQL query arguments, ensures it's a SELECT query, executes it using the MySQL connection pool, and returns the results as JSON or an error message.

  private async handleReadQuery(request: any, transactionId: string) {
    if (!isValidSqlQueryArgs(request.params.arguments)) {
      throw new McpError(
        ErrorCode.InvalidParams,
        'SQL 查询参数无效。'
      );
    }
  
    const query = request.params.arguments.query;
  
    if (!isReadOnlyQuery(query)) {
      throw new McpError(
        ErrorCode.InvalidParams,
        'run_sql_query 工具仅允许 SELECT 查询。'
      );
    }
  
    console.error(`[${transactionId}] 执行 SELECT 查询: ${query}`);
  
    try {
      const [rows] = await this.pool.query(query);
      console.error(`[${transactionId}] 查询执行成功`);
  
      return {
        content: [
          {
            type: 'text',
            text: JSON.stringify(rows, null, 2),
          },
        ],
      };
    } catch (error) {
      console.error(`[${transactionId}] 查询出错:`, error);
      if (error instanceof Error) {
        return {
          content: [
            {
              type: 'text',
              text: `MySQL 错误: ${error.message}`,
            },
          ],
          isError: true,
        };
      }
      throw error;
    }
  }

• src/index.ts:102-115 (schema)

  Tool schema definition including input schema for 'query' parameter, provided in the ListTools response.

  {
    name: 'run_sql_query',
    description: '执行只读 SQL 查询（仅限 SELECT 语句）',
    inputSchema: {
      type: 'object',
      properties: {
        query: {
          type: 'string',
          description: '要执行的 SQL SELECT 查询语句',
        },
      },
      required: ['query'],
    },
  },

• src/index.ts:190-214 (registration)

  Tool call request handler that dispatches to handleReadQuery based on tool name 'run_sql_query'.

  this.server.setRequestHandler(CallToolRequestSchema, async (request) => {
    const transactionId = generateTransactionId();
    console.error(`[${transactionId}] 正在处理请求: ${request.params.name}`);
  
    // 根据工具类型分发处理
    switch (request.params.name) {
      case 'run_sql_query':
        return this.handleReadQuery(request, transactionId);
      case 'create_table':
        return this.handleCreateTable(request, transactionId);
      case 'insert_data':
        return this.handleInsertData(request, transactionId);
      case 'update_data':
        return this.handleUpdateData(request, transactionId);
      case 'delete_data':
        return this.handleDeleteData(request, transactionId);
      case 'execute_sql':
        return this.handleExecuteSql(request, transactionId);
      default:
        throw new McpError(
          ErrorCode.MethodNotFound,
          `未知工具: ${request.params.name}`
        );
    }
  });

• src/index.ts:21-33 (helper)

  Helper functions and interface for validating SQL query arguments and checking if it's a read-only SELECT query.

  interface SqlQueryArgs {
    query: string;
  }
  
  // 校验 SQL 查询参数是否合法
  const isValidSqlQueryArgs = (args: any): args is SqlQueryArgs =>
    typeof args === 'object' &&
    args !== null &&
    typeof args.query === 'string';
  
  // 判断是否为只读查询（SELECT）
  const isReadOnlyQuery = (query: string): boolean =>
    query.trim().toLowerCase().startsWith('select');