MCP-MySQL Server

Instructions

Implementation Reference

• src/index.ts:651-684 (handler)

  The handler function that implements the describe_table tool by querying the INFORMATION_SCHEMA.COLUMNS table to retrieve and format the table structure.

  private async handleDescribeTable(args: any) {
    if (!args.table) {
      throw new McpError(ErrorCode.InvalidParams, 'Table name is required');
    }
  
    const rows = await this.executeQuery(
      `SELECT 
        COLUMN_NAME as Field,
        COLUMN_TYPE as Type,
        IS_NULLABLE as \`Null\`,
        COLUMN_KEY as \`Key\`,
        COLUMN_DEFAULT as \`Default\`,
        EXTRA as Extra,
        COLUMN_COMMENT as Comment
      FROM INFORMATION_SCHEMA.COLUMNS 
      WHERE TABLE_SCHEMA = ? AND TABLE_NAME = ?
      ORDER BY ORDINAL_POSITION`,
      [this.config!.database, args.table]
    );
  
    const formattedRows = (rows as any[]).map(row => ({
      ...row,
      Null: row.Null === 'YES' ? 'YES' : 'NO'
    }));
  
    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify(formattedRows, null, 2),
        },
      ],
    };
  }

• src/index.ts:479-488 (schema)

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

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

• src/index.ts:476-489 (registration)

  Registration of the describe_table tool in the ListTools response, including name, description, and input schema.

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

• src/index.ts:579-580 (registration)

  Dispatcher case in CallToolRequest handler that routes 'describe_table' calls to the handleDescribeTable method.

  case 'describe_table':
    return await this.handleDescribeTable(request.params.arguments);