Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real value beyond that: an importance scale ('higher is more important') and the caveat that tentative dates may move, which tells the agent how much to trust the output. It says nothing about the look-ahead window or how the limit is applied.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.