Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, so safety is covered. The description adds behavioral context beyond the annotation: it scopes to the authenticated account's tasklists and indicates that the returned IDs are meant to be passed on to other tools. This tells the agent the output is a set of tasklists with IDs, which is useful for chaining. No additional risk or side-effect info is needed given the read-only nature.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.