Nearly half of MCP servers expose tools an agent could plausibly confuse

A reader made a point on my last post that I couldn't answer at the time, so I went and measured it. The point: "tool added" is not automatically a safe change. I'd been filing additions under harmless because every old invocation still validates against its schema. But validation isn't selection. A new overlapping tool can capture calls that used to route somewhere else, and nothing errors — the agent just quietly starts doing something different. I said name-overlap was the obvious first…