import path from 'path';
import express, { type Express, type Request, type Response } from 'express';
import type { McpConfig } from './config';
import type { ToolFromOpenApi } from './openapi-to-tools';
// Load SDK via explicit .js paths to avoid Node resolution bug with package exports wildcard.
// Use path relative to this file so it works in Docker and when running from dist/.
const sdkRoot = path.join(__dirname, '..', 'node_modules', '@modelcontextprotocol', 'sdk');
const { McpServer } = require(path.join(sdkRoot, 'dist/cjs/server/mcp.js'));
const { StreamableHTTPServerTransport } = require(path.join(sdkRoot, 'dist/cjs/server/streamableHttp.js'));
/**
* Creates an Express app that serves MCP over Streamable HTTP at POST /mcp and GET /mcp.
* Tools are built from OpenAPI spec (loaded at startup). Stateless: each request gets a new McpServer and transport.
*/
export function createMcpApp(config: McpConfig, tools: ToolFromOpenApi[]): Express {
const app = express();
app.use(express.json());
type ToolCb = (args: unknown, extra: unknown) => Promise<{ content: Array<{ type: 'text'; text: string }>; isError?: boolean }>;
async function handleMcpRequest(req: Request, res: Response): Promise<void> {
const server = new McpServer(
{
name: config.serverName,
version: '1.0.0',
},
{ capabilities: { tools: {} } },
);
for (const tool of tools) {
(server as { registerTool(name: string, config: { description: string; inputSchema: unknown }, cb: ToolCb): void }).registerTool(
tool.name,
{ description: tool.description, inputSchema: tool.inputSchema },
(args, _extra) => tool.handler(args as Record<string, unknown>),
);
}
const transport = new StreamableHTTPServerTransport({
sessionIdGenerator: undefined,
});
await server.connect(transport);
res.on('close', () => {
transport.close().catch(() => {});
server.close().catch(() => {});
});
try {
await transport.handleRequest(req as never, res as never, req.body);
} catch (err) {
console.error('[mcp] handleRequest error:', err);
if (!res.headersSent) {
res.status(500).json({
jsonrpc: '2.0',
error: { code: -32603, message: (err as Error).message },
id: null,
});
}
}
}
app.post('/mcp', (req: Request, res: Response) => void handleMcpRequest(req, res));
app.get('/mcp', (req: Request, res: Response) => void handleMcpRequest(req, res));
return app;
}
