MCP PostgreSQL Server

Instructions

Implementation Reference

• src/index.ts:278-316 (handler)

  The main execution handler for the 'connect_db' tool. Validates input parameters, closes any existing database connection, updates the configuration, establishes a new connection via ensureConnection(), and returns a success response or throws an error.

  private async handleConnectDb(args: any) {
    if (!args.host || !args.user || !args.password || !args.database) {
      throw new McpError(
        ErrorCode.InvalidParams,
        'Missing required database configuration parameters'
      );
    }
  
    // Close existing connection if any
    if (this.client) {
      await this.client.end();
      this.client = null;
    }
  
    this.config = {
      host: args.host,
      port: args.port || 5432,
      user: args.user,
      password: args.password,
      database: args.database,
    };
  
    try {
      await this.ensureConnection();
      return {
        content: [
          {
            type: 'text',
            text: 'Successfully connected to PostgreSQL database',
          },
        ],
      };
    } catch (error) {
      throw new McpError(
        ErrorCode.InternalError,
        `Failed to connect to database: ${getErrorMessage(error)}`
      );
    }
  }

• src/index.ts:142-167 (schema)

  Defines the input schema for the 'connect_db' tool, specifying properties for database connection details and required fields.

  inputSchema: {
    type: 'object',
    properties: {
      host: {
        type: 'string',
        description: 'Database host',
      },
      port: {
        type: 'number',
        description: 'Database port (default: 5432)',
      },
      user: {
        type: 'string',
        description: 'Database user',
      },
      password: {
        type: 'string',
        description: 'Database password',
      },
      database: {
        type: 'string',
        description: 'Database name',
      },
    },
    required: ['host', 'user', 'password', 'database'],
  },

• src/index.ts:139-168 (registration)

  Registers the 'connect_db' tool in the ListTools handler, including its name, description, and input schema.

  {
    name: 'connect_db',
    description: 'Connect to PostgreSQL database. NOTE: Default connection exists - only use when requested or if other commands fail',
    inputSchema: {
      type: 'object',
      properties: {
        host: {
          type: 'string',
          description: 'Database host',
        },
        port: {
          type: 'number',
          description: 'Database port (default: 5432)',
        },
        user: {
          type: 'string',
          description: 'Database user',
        },
        password: {
          type: 'string',
          description: 'Database password',
        },
        database: {
          type: 'string',
          description: 'Database name',
        },
      },
      required: ['host', 'user', 'password', 'database'],
    },
  },

• src/index.ts:257-258 (registration)

  In the CallTool request handler switch statement, dispatches 'connect_db' calls to the handleConnectDb method.

  case 'connect_db':
    return await this.handleConnectDb(request.params.arguments);