The Model Context Protocol made it ordinary for an agent host to discover tools and dispatch calls. What it did not standardise is trust. A host still tends to take a server identity and a self-declar
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This is a crucial distinction that often gets lost in MCP discussions. Server admission is about trust at the connection layer, whereas tool-call permission is about runtime authorization scoped to specific capabilities. One pattern that addresses this cleanly is binding tool-level grants to session keys with finite lifetimes, so each connection carries its own permission set rather than inheriting blanket access from the admission handshake. That way you admit a server once but still enforce per-invocation constraints on which tools it can actually call.
the two gates framing is right. from the other end: building grunz (coding agent on open models) we originally shipped with a handful of MCP servers switched on by default and ended up turning all of them off, because they were causing weird glitches we couldn't trace back to anything the user actually asked for. deny by default at admission would have saved us the trouble. the tool-call gate also matters more with open or abliterated models, since prompt level "don't call X" instructions are exactly what those follow less reliably. is the allowlist per project or per user in your setup?
indiainfranotes
Admitting an MCP server once and treating that as forever tool permission is how agent hosts quietly accumulate god-mode. Session-scoped tool grants with short lifetimes keep the connection handshake separate from what the model can invoke this turn. Deny-by-default at admission also saves the weird tool calls nobody asked for. Are your allowlists per project, per user, or still a shared JSON file copied from a README?