Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds genuine context beyond them: the score scale (0-100) and the important edge case that the composite is null when nothing has been measured yet. It does not cover freshness/staleness or whether a score must first be generated, so not a full 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.