Excellent write-up and understanding of the current state of MCP
I’ve been waiting for someone to point it out. This is in my opinion the biggest limitation of the current spec.
What is needed is a tool invocation context that is provided at tool invocation time.
Such tool invocation context allows passing information that would allow authorizing, authentication but also tracing the original “requester”: think of it as “tool invoked on behalf of user identity”
This of course implies an upstream authnz that feeds these details and more.
If you’re interested in this topic, my email is in my bio: I’m of the architect of our multi-tenant tool calling implementation that we’ve been running in production for the past year with enterprise customers where authnz and auditability are key requirements.