Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
readOnlyHint=true already tells the agent this is a safe, non-mutating call, so the description needs to add operational context it does not: what the check actually returns, whether it is cheap or triggers a subprocess/install detection, or whether it caches. The parenthetical hints at an environment dependency but never explains the resulting behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.