describe_table

Instructions

Implementation Reference

• src/index.ts:441-469 (handler)

  The handler function for 'describe_table' tool. Ensures database connection, validates table name, executes 'DESCRIBE ??' query using prepared statement, and returns the table structure as JSON.

  private async handleDescribeTable(requestId: string, args: any) {
    await this.ensureConnection();
  
    if (!args.table) {
      throw new McpError(ErrorCode.InvalidParams, 'Table name is required');
    }
  
    try {
      console.error(`[${requestId}] Executing DESCRIBE ${args.table}`);
      const [rows] = await this.pool!.query('DESCRIBE ??', [args.table]);
      console.error(`[${requestId}] DESCRIBE completed, found ${Array.isArray(rows) ? rows.length : 0} columns`);
  
      return {
        content: [
          {
            type: 'text',
            text: JSON.stringify(rows, null, 2),
          },
        ],
      };
    } catch (error) {
      const errorMsg = getErrorMessage(error);
      console.error(`[${requestId}] Failed to describe table: ${errorMsg}`);
      throw new McpError(
        ErrorCode.InternalError,
        `Failed to describe table: ${errorMsg}`
      );
    }
  }

• src/index.ts:250-263 (schema)

  Input schema for the 'describe_table' tool, defining a required 'table' string parameter.

  {
    name: 'describe_table',
    description: 'Get table structure',
    inputSchema: {
      type: 'object',
      properties: {
        table: {
          type: 'string',
          description: 'Table name',
        },
      },
      required: ['table'],
    },
  },

• src/index.ts:299-301 (registration)

  Registration in the CallToolRequestHandler switch statement, routing 'describe_table' calls to the handleDescribeTable method.

  case 'describe_table':
    result = await this.handleDescribeTable(requestId, request.params.arguments);
    break;

• src/index.ts:183-265 (registration)

  Tool list registration in ListToolsRequestHandler, including 'describe_table' with its schema for tool discovery.

  this.server.setRequestHandler(ListToolsRequestSchema, async () => ({
    tools: [
      {
        name: 'connect_db',
        description: 'Connect to MySQL database (optional if environment variables are set)',
        inputSchema: {
          type: 'object',
          properties: {
            host: {
              type: 'string',
              description: 'Database host',
            },
            user: {
              type: 'string',
              description: 'Database user',
            },
            password: {
              type: 'string',
              description: 'Database password',
            },
            database: {
              type: 'string',
              description: 'Database name',
            },
            port: {
              type: 'number',
              description: 'Database port (optional)',
            },
          },
          required: ['host', 'user', 'password', 'database'],
        },
      },
      {
        name: 'query',
        description: 'Execute a SELECT query',
        inputSchema: {
          type: 'object',
          properties: {
            sql: {
              type: 'string',
              description: 'SQL SELECT query',
            },
            params: {
              type: 'array',
              items: {
                type: ['string', 'number', 'boolean', 'null'],
              },
              description: 'Query parameters (optional)',
            },
          },
          required: ['sql'],
        },
      },
      {
        name: 'list_tables',
        description: 'List all tables in the database',
        inputSchema: {
          type: 'object',
          properties: {
            random_string: {
              type: 'string',
              description: 'Dummy parameter for no-parameter tools',
            }
          },
          required: [], // 修改为可选参数
        },
      },
      {
        name: 'describe_table',
        description: 'Get table structure',
        inputSchema: {
          type: 'object',
          properties: {
            table: {
              type: 'string',
              description: 'Table name',
            },
          },
          required: ['table'],
        },
      },
    ],
  }));