71,929 to 581 tokens is a brutal number to see once someone actually measures it — the "silent context tax" framing is exactly right, because most people (myself included, before reading this) assume the cost only shows up when a tool actually executes, not on every single idle turn just for the model to know the tool exists.

To answer your question: I've been connecting MCP servers across a few different agent contexts recently — registry-based discovery for agent payment/commerce tools (x402-adjacent work) and some coding-agent workflow tooling. The config-silo problem you describe is real even outside Cursor/Claude Code specifically — anywhere a tool definition needs to be declared once but consumed by multiple clients with different expected schemas, you get the same duplicate-JSON-files failure mode. I hadn't quantified the idle-turn token cost before, so seeing it benchmarked this concretely is genuinely useful.

One thing I'm curious about on the lazy-hydration side: when the gateway swaps a compact name for the full schema on tool selection, how does it handle a server whose tool schema actually changes between the name-index being cached and the moment of selection (e.g. a server that's mid-deploy, or a remote SSE endpoint that updates its own tool list)? Does the gateway re-validate against the live server at hydration time, or is there a risk of the model selecting a tool by a name whose underlying contract has already drifted?

On the project itself — since mcptoon is sitting at ~200 stars and solving a problem basically everyone with a multi-tool setup will eventually hit, there's a reasonably clear monetization path if you wanted to pursue it: keep the local sync/CLI free and open, but offer a small hosted tier for teams — shared server declarations across a whole team's machines, audit logging of what got hydrated when, or managed name-index caching for larger toolchains than a solo dev would hit. That's roughly the open-core shape a few other dev-tooling projects in this space have taken, and the "single source of truth synced to every client" pitch sells itself to a team lead who's tired of onboarding new hires onto 4 different JSON configs by hand.

Solid writeup — going to look at mcptoon for my own setup.