MCP MySQL Server

Instructions

Implementation Reference

• src/index.ts:667-688 (handler)

  The handler function that implements the add_column tool. It constructs an ALTER TABLE ADD COLUMN SQL statement based on the input arguments and executes it using the shared executeQuery method.

  private async handleAddColumn(args: any) {
    if (!args.table || !args.field) {
      throw new McpError(ErrorCode.InvalidParams, 'Table name and field are required');
    }
  
    let sql = `ALTER TABLE \`${args.table}\` ADD COLUMN \`${args.field.name}\` ${args.field.type.toUpperCase()}`;
    if (args.field.length) sql += `(${args.field.length})`;
    if (args.field.nullable === false) sql += ' NOT NULL';
    if (args.field.default !== undefined) {
      sql += ` DEFAULT ${args.field.default === null ? 'NULL' : `'${args.field.default}'`}`;
    }
  
    await this.executeQuery(sql);
    return {
      content: [
        {
          type: 'text',
          text: `Column ${args.field.name} added to table ${args.table}`
        }
      ]
    };
  }

• src/index.ts:489-513 (registration)

  Registers the 'add_column' tool in the listTools response, including its description and input schema definition.

  {
    name: 'add_column',
    description: 'Add a new column to existing table',
    inputSchema: {
      type: 'object',
      properties: {
        table: { type: 'string' },
        field: {
          type: 'object',
          properties: {
            name: { type: 'string' },
            type: { type: 'string' },
            length: { type: 'number', optional: true },
            nullable: { type: 'boolean', optional: true },
            default: {
              type: ['string', 'number', 'null'],
              optional: true
            }
          },
          required: ['name', 'type']
        }
      },
      required: ['table', 'field']
    }
  }

• src/index.ts:531-532 (registration)

  In the CallToolRequest handler switch statement, routes 'add_column' tool calls to the handleAddColumn method.

  case 'add_column':
    return await this.handleAddColumn(request.params.arguments);