Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide basic hints (not read-only, not idempotent, not destructive). The description adds the timing constraint, which is key behavioral context. However, it does not expand on other behavioral aspects like message delivery guarantees 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.