MySQL MCP Server

Instructions

Implementation Reference

• src/index.ts:136-149 (registration)

  Tool registration in the listTools response, defining name, description, and input schema for 'update_data'.

  {
    name: 'update_data',
    description: 'Updates data in a table in the MySQL database.',
    inputSchema: {
      type: 'object',
      properties: {
        query: {
          type: 'string',
          description: 'The SQL UPDATE query to execute.',
        },
      },
      required: ['query'],
    },
  },

• src/index.ts:193-194 (registration)

  Dispatch registration in the CallToolRequest handler switch statement, routing 'update_data' to its handler.

  case 'update_data':
    return this.handleUpdateData(request, transactionId);

• src/index.ts:364-414 (handler)

  Core handler implementation for 'update_data': validates arguments and query type, executes UPDATE on MySQL pool, returns formatted success/error response.

  private async handleUpdateData(request: any, transactionId: string) {
    if (!isValidSqlQueryArgs(request.params.arguments)) {
      throw new McpError(
        ErrorCode.InvalidParams,
        'Invalid SQL query arguments.'
      );
    }
  
    const query = request.params.arguments.query;
    
    if (!isUpdateQuery(query)) {
      throw new McpError(
        ErrorCode.InvalidParams,
        'Only UPDATE queries are allowed with update_data tool.'
      );
    }
  
    console.error(`[${transactionId}] Executing UPDATE query: ${query}`);
    
    try {
      const [result] = await this.pool.query(query);
      console.error(`[${transactionId}] Data updated successfully`);
      
      return {
        content: [
          {
            type: 'text',
            text: JSON.stringify({
              success: true,
              message: 'Data updated successfully',
              result
            }, null, 2),
          },
        ],
      };
    } catch (error) {
      console.error(`[${transactionId}] Query error:`, error);
      if (error instanceof Error) {
        return {
          content: [
            {
              type: 'text',
              text: `MySQL error: ${error.message}`,
            },
          ],
          isError: true,
        };
      }
      throw error;
    }
  }

• src/index.ts:42-44 (helper)

  Helper function used by update_data handler to validate if the provided query starts with 'update'.

  const isUpdateQuery = (query: string): boolean => 
    query.trim().toLowerCase().startsWith('update');