I don't understand the logistics of MCP interactions. Can anyone explain why they aren't stateless. Why does a connection need to be held open?
In practice, nobody uses those parts of the protocol (it was overdesigned and hardly any clients support it). The key thing MCP brings right now is a standardized way to discover & invoke tools. This would’ve worked equally well as a plain HTTP-based protocol (certainly for a v1) and it’d have made it 10x easier to implement.
With plain HTTP you can quite easily "stream" both the request's and the response's body: that's a HTTP/1 feature called "chunking" (the message body is not just one byte array, it's "chunked" so that each chunk can be received in sequence). I really don't get why people think you need WS (or ffs SSE) for "streaming". I've implemented a chat using just good old HTTP/1.1 with chunking. It's actually a perfect use case, so it suits LLMs quite well.
For example, you have a MCP client (let's say it's amazon q cli), a you have a MCP server for executing commands over ssh. If connection is maintained between MCP client and server, then MCP server can keep ssh connection alive.
Replace SSH server with anything else that has state - a browser for example (now your AI assistant also can have 500 open tabs)