MCP Universal DB Client

#!/usr/bin/env node import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js"; import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js"; import { z } from "zod/v3"; import { connectDatabaseInputSchema, DatabaseConnections } from "./connection"; import { sql } from "kysely"; import { analyzeQueryType } from "./analyzer"; import { makeError, makeSuccess } from "./response"; const mcpServer = new McpServer({ name: "mcp-universal-db-client", version: "0.0.0", }); const databaseConnections = new DatabaseConnections(); 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)`, }, ], }; } ); mcpServer.registerTool( "list_connections", { title: "List Connections", description: "List all active database connections", }, async () => { const connections = databaseConnections.getAllConnections(); return { content: [ { type: "text", text: JSON.stringify({ connections: connections, }), }, ], }; } ); mcpServer.registerTool( "disconnect_database", { title: "Disconnect Database", description: "Disconnect from a database using connection ID", inputSchema: { connectionID: z.string().describe("The connection ID to disconnect"), }, }, async (input) => { databaseConnections.deleteConnection(input.connectionID); return { content: [ { type: "text", text: `Disconnected connection ID: ${input.connectionID}`, }, ], }; } ); mcpServer.registerTool( "disconnect_all", { title: "Disconnect All", description: "Disconnect all active database connections", }, async () => { await databaseConnections.deleteAllConnections(); return { content: [ { type: "text", text: "All connections have been disconnected.", }, ], }; } ); mcpServer.registerTool( "query_read", { title: "Run Read-Only SQL Query", description: "Run SELECT and other read-only SQL queries on the connected database. This tool only accepts non-destructive queries (SELECT, SHOW, DESCRIBE, EXPLAIN).", inputSchema: { connectionID: z.string().describe("The connection ID"), query: z .string() .array() .describe("The SQL queries to execute (read-only operations only)"), }, }, async (input) => { try { const connection = databaseConnections.getConnection(input.connectionID); const results = await executeQueries(connection, input.query, { readonly: true, }); return makeSuccess( results, "Rows are the results of the structured query results, so show them in a table format if possible." ); } catch (error) { return makeError(error); } } ); mcpServer.registerTool( "query_write", { title: "Run Destructive SQL Query", description: "Run INSERT, UPDATE, DELETE and other destructive SQL queries on the connected database. Use with caution as this can modify data.", inputSchema: { connectionID: z.string().describe("The connection ID"), query: z .string() .array() .describe("The SQL queries to execute (INSERT, UPDATE, DELETE, etc.)"), }, }, async (input) => { try { const connection = databaseConnections.getConnection(input.connectionID); const results = await executeQueries(connection, input.query); return makeSuccess(results, "Query executed successfully."); } catch (error) { return makeError(error); } } ); /** * クエリを実行するヘルパー関数 */ const executeQueries = async ( connection: ReturnType<typeof databaseConnections.getConnection>, queries: string[], options?: { readonly?: boolean; } ) => { const results = []; for (const query of queries) { // 読み取り専用検証（オプション） if (options?.readonly) { const queryType = analyzeQueryType(query); if (queryType !== "read") { throw new Error( `Destructive query detected. Use query_write instead.\nQuery: ${query}` ); } } // クエリ実行 const q = sql.raw(query).compile(connection!.instance); const result = await connection!.instance.executeQuery(q); results.push({ query, res: result }); } return results; }; const main = async () => { const transport = new StdioServerTransport(); await mcpServer.connect(transport); }; main().catch((err) => { console.error(err); process.exit(1); });