Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and destructiveHint=false, so the description's 'without persisting anything' and 'Read-only' largely duplicate that safety profile. It adds the straight-line calculation method but does not disclose additional behavioral traits such as failure modes, auth requirements, or precisely how startDate affects the result.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.