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), so the description only needs to add beyond that. It does add meaningful context: retained source decimals, missing values, preliminary/revision footnotes and evidence, non-real-time cadence, and 'not independently verified'. Auth/permissions and rate limits are not mentioned, 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.