Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, and closed-world, so safety is covered; the description adds that the return is full markdown content rather than a snippet, which is useful behavioral context. It stops short of noting any truncation limits or page-size behavior, keeping it from a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.