Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare read-only, idempotent, closed-world, non-destructive behavior, so the description does not need to repeat safety traits. It adds genuinely useful behavioral context: results are newest first, include status and URLs, and require OAuth or an API key header. It does not describe rate limits or pagination beyond the limit parameter, but it covers the most important operational constraints.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.