MCP SQL Server

Instructions

Implementation Reference

• index.js:245-329 (handler)

  The core handler function for the 'connect_database' tool. It merges user-provided config with environment variables, disconnects any existing connection, initializes a connection pool for PostgreSQL or MySQL, tests the connection, and returns a success message.
  async connectDatabase(config) { // Merge with environment variables if config is partial let finalConfig; if (!config.type || !config.host || !config.port || !config.database || !config.user || !config.password) { // Try to get missing values from env const envConfig = this.getConfigFromEnv(); if (!envConfig) { throw new Error( 'Incomplete database configuration. Provide all parameters or set environment variables:\n' + 'For PostgreSQL: DB_TYPE=postgresql, DB_HOST, DB_PORT, DB_DATABASE, DB_USER, DB_PASSWORD\n' + 'For MySQL: DB_TYPE=mysql, MYSQL_HOST, MYSQL_PORT, MYSQL_DATABASE, MYSQL_USER, MYSQL_PASSWORD' ); } // Merge provided config with env config (provided values take precedence) finalConfig = { type: config.type || envConfig.type, host: config.host || envConfig.host, port: config.port || envConfig.port, database: config.database || envConfig.database, user: config.user || envConfig.user, password: config.password || envConfig.password, ssl: config.ssl !== undefined ? config.ssl : envConfig.ssl, }; } else { finalConfig = config; } // Disconnect existing connections await this.disconnectDatabase(); this.currentConfig = finalConfig; if (finalConfig.type === 'postgresql') { this.postgresPool = new Pool({ host: finalConfig.host, port: finalConfig.port, database: finalConfig.database, user: finalConfig.user, password: finalConfig.password, ssl: finalConfig.ssl ? { rejectUnauthorized: false } : false, max: 10, }); // Test connection const client = await this.postgresPool.connect(); await client.query('SELECT NOW()'); client.release(); return { content: [ { type: 'text', text: `Successfully connected to PostgreSQL database: ${finalConfig.database}@${finalConfig.host}:${finalConfig.port}`, }, ], }; } else if (finalConfig.type === 'mysql') { this.mysqlConnection = mysql.createPool({ host: finalConfig.host, port: finalConfig.port, database: finalConfig.database, user: finalConfig.user, password: finalConfig.password, ssl: finalConfig.ssl ? {} : undefined, waitForConnections: true, connectionLimit: 10, }); // Test connection await this.mysqlConnection.query('SELECT NOW()'); return { content: [ { type: 'text', text: `Successfully connected to MySQL database: ${finalConfig.database}@${finalConfig.host}:${finalConfig.port}`, }, ], }; } else { throw new Error(`Unsupported database type: ${finalConfig.type}`); } }
• index.js:116-151 (schema)

  Input schema defining the parameters for connecting to a database: type (postgresql/mysql), host, port, database, user, password, ssl.
  inputSchema: { type: 'object', properties: { type: { type: 'string', enum: ['postgresql', 'mysql'], description: 'Database type (optional if using env vars)', }, host: { type: 'string', description: 'Database host (optional if using env vars)', }, port: { type: 'number', description: 'Database port (optional if using env vars)', }, database: { type: 'string', description: 'Database name (optional if using env vars)', }, user: { type: 'string', description: 'Database user (optional if using env vars)', }, password: { type: 'string', description: 'Database password (optional if using env vars)', }, ssl: { type: 'boolean', description: 'Use SSL connection (optional)', default: false, }, }, required: [], },
• index.js:112-152 (registration)

  Tool registration in the ListToolsRequestSchema handler, including name, description, and input schema.
  { name: 'connect_database', description: 'Connect to a PostgreSQL or MySQL database. Parameters can be provided directly or loaded from environment variables. If no parameters are provided, will use environment variables (DB_TYPE, DB_HOST, DB_PORT, DB_DATABASE, DB_USER, DB_PASSWORD, DB_SSL). For PostgreSQL: POSTGRES_HOST, POSTGRES_PORT, etc. For MySQL: MYSQL_HOST, MYSQL_PORT, etc.', inputSchema: { type: 'object', properties: { type: { type: 'string', enum: ['postgresql', 'mysql'], description: 'Database type (optional if using env vars)', }, host: { type: 'string', description: 'Database host (optional if using env vars)', }, port: { type: 'number', description: 'Database port (optional if using env vars)', }, database: { type: 'string', description: 'Database name (optional if using env vars)', }, user: { type: 'string', description: 'Database user (optional if using env vars)', }, password: { type: 'string', description: 'Database password (optional if using env vars)', }, ssl: { type: 'boolean', description: 'Use SSL connection (optional)', default: false, }, }, required: [], }, },
• index.js:213-214 (registration)

  Dispatch logic in the CallToolRequestSchema handler that routes 'connect_database' calls to the connectDatabase method.
  case 'connect_database': return await this.connectDatabase(args);
• index.js:38-95 (helper)

  Supporting utility to extract and validate database configuration from various environment variable formats for both PostgreSQL and MySQL.
  getConfigFromEnv() { // Check for PostgreSQL env vars const pgHost = process.env.DB_HOST || process.env.POSTGRES_HOST; const pgPort = process.env.DB_PORT || process.env.POSTGRES_PORT; const pgDatabase = process.env.DB_DATABASE || process.env.POSTGRES_DATABASE; const pgUser = process.env.DB_USER || process.env.POSTGRES_USER; const pgPassword = process.env.DB_PASSWORD || process.env.POSTGRES_PASSWORD; const dbType = process.env.DB_TYPE || process.env.DATABASE_TYPE; // Check for MySQL env vars const mysqlHost = process.env.MYSQL_HOST; const mysqlPort = process.env.MYSQL_PORT; const mysqlDatabase = process.env.MYSQL_DATABASE; const mysqlUser = process.env.MYSQL_USER; const mysqlPassword = process.env.MYSQL_PASSWORD; // Determine database type let type = null; if (dbType) { type = dbType.toLowerCase() === 'mysql' ? 'mysql' : 'postgresql'; } else if (mysqlHost || mysqlDatabase) { type = 'mysql'; } else if (pgHost || pgDatabase) { type = 'postgresql'; } if (!type) { return null; } if (type === 'postgresql') { if (!pgHost || !pgPort || !pgDatabase || !pgUser || !pgPassword) { return null; } return { type: 'postgresql', host: pgHost, port: parseInt(pgPort, 10), database: pgDatabase, user: pgUser, password: pgPassword, ssl: process.env.DB_SSL === 'true' || process.env.POSTGRES_SSL === 'true', }; } else { if (!mysqlHost || !mysqlPort || !mysqlDatabase || !mysqlUser || !mysqlPassword) { return null; } return { type: 'mysql', host: mysqlHost, port: parseInt(mysqlPort, 10), database: mysqlDatabase, user: mysqlUser, password: mysqlPassword, ssl: process.env.DB_SSL === 'true' || process.env.MYSQL_SSL === 'true', }; } }