The lack of some form of session setup process in the core protocol (not the current 'session' setup that negotiates the protocol) is certainly a PITA. I've been working on using MCP in a multi-tenant setup and it basically means I can't use any MCP Server as delivered at this point. Conceptually MCP is great. In certain single-user scenarios it is great. I think it'll eventually be great for me once the use case of "multi-tenant gateway service" becomes feasible.