Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), so the description's added value is the disclosure that cost/duration benchmarks return coming_soon with null estimates instead of the manual wizard defaults. That is exactly the kind of behavioral caveat an agent needs to avoid misinterpreting placeholder output. It does not mention rate limits or auth, but those are minor here.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.