Websocket transport?

[geelen]

Is your feature request related to a problem? Please describe.

Experimenting with writing MCP Servers in Cloudflare Workers/Durable Objects. Currently doing a simple pivot from stdin/stderr to HTTP, e.g.

server.setRequestHandler(ListToolsRequestSchema, async () => {
  const { url } = await serverReady
  const resp = await fetch(`${url}/tools/list`)
  return resp.json()
})

server.setRequestHandler(CallToolRequestSchema, async (request) => {
  const { name, arguments: args } = request.params
  const { url } = await serverReady
  const resp = await fetch(`${url}/tools/call/${name}`, {
    method: 'POST',
    body: JSON.stringify(args)
  })
  return resp.json()
})

Describe the solution you'd like

It would be a bit neater if I could do something like:

// On the local server
const serverReady = await // boot something locally or get an auth token for remote
const proxy = new TransportProxy()
const localTransport = new StdioServerTransport()
const wsTransport = new WebsocketTransport({ url: serverReady.wssUrl })
await proxy.connect(localTransport, wsTransport)

// Inside the worker
const webSocketPair = new WebSocketPair();
const client = webSocketPair[0], server = webSocketPair[1];

const transport = new WebsocketTransport({ connection: server })
this.ctx.waitUntil(server.connect(transport))

return new Response(null, {
  status: 101,
  webSocket: client,
});

The issue with making this completely generic is being able to establish the websocket in a secure way. I can see the advantage of stdin/stdout in that respect! But I thought I'd raise the issue to see if there'd been interest in using websockets like this?

Describe alternatives you've considered

Making Claude Desktop config allow a "websocket" URL instead of a "command", and a "headers" field instead of "args" for auth? That sounds like the end goal, but this might be a good stopgap.

Additional context

I am also not sure if @modelcontextprotocol/sdk works out of the box in Cloudflare Workers, but that should be a fairly easy fix.