Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations cover the safety profile (destructiveHint=false, openWorldHint=false, idempotentHint=false), and the description adds genuinely useful context beyond them: the report is public, it is checked like any other claim, and it never mutates data by itself. It stops short of noting auth needs or rate limits.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.