MCP Universal DB Client

Instructions

Implementation Reference

• src/index.ts:24-39 (handler)

  Handler function for the "connect_database" tool. It adds the connection using DatabaseConnections.addConnection and returns a confirmation message with the connection name.

  async (input) => {
    databaseConnections.addConnection(input);
  
    return {
      content: [
        {
          type: "text",
          text: `Connected to ${input.dialect} database.`,
        },
        {
          type: "text",
          text: `Connection Name: ${input.name} (use this name for future queries)`,
        },
      ],
    };
  }

• src/connection.ts:11-21 (schema)

  Zod input schema for the connect_database tool, defining name, dialect, and connectionString fields.

  export const connectDatabaseInputSchema = z.object({
    name: z
      .string()
      .describe("An unique name for this connection to be used as an ID"),
    dialect: dialectsSchema,
    connectionString: z
      .string()
      .describe(
        "The database connection string. e.g., postgresql://user:password@localhost:5432/dbname"
      ),
  });

• src/index.ts:17-40 (registration)

  Registration of the "connect_database" tool on the MCP server, specifying title, description, input schema, and handler.

  mcpServer.registerTool(
    "connect_database",
    {
      title: "Connect Database",
      description: "Connect to a database using connection string",
      inputSchema: connectDatabaseInputSchema.shape,
    },
    async (input) => {
      databaseConnections.addConnection(input);
  
      return {
        content: [
          {
            type: "text",
            text: `Connected to ${input.dialect} database.`,
          },
          {
            type: "text",
            text: `Connection Name: ${input.name} (use this name for future queries)`,
          },
        ],
      };
    }
  );

• src/connection.ts:63-71 (helper)

  addConnection method in DatabaseConnections class, called by the handler to create and store the Kysely database instance.

  public addConnection(input: ConnectDatabaseInput) {
    this.connections.set(input.name, {
      instance: new Kysely({
        dialect: createDialect(input),
      }),
      dialect: input.dialect,
      connectedAt: new Date(),
    });
  }

• src/connection.ts:25-46 (helper)

  createDialect helper function that initializes the appropriate Kysely dialect (Postgres, MySQL, SQLite) based on input.

  export const createDialect = (input: ConnectDatabaseInput) => {
    switch (input.dialect) {
      case "psql":
        return new PostgresDialect({
          pool: new Pool({
            connectionString: input.connectionString,
          }),
        });
      case "mysql":
        return new MysqlDialect({
          pool: createPool({
            uri: input.connectionString,
          }),
        });
      case "sqlite":
        return new SqliteDialect({
          database: new Database(input.connectionString),
        });
      default:
        throw new Error(`Unsupported dialect: ${input.dialect}`);
    }
  };