Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds useful context beyond that: each entry includes its cookbooks, the user's note, and last-cooked time/count as recorded by mark_cooked, which tells the agent what fields are meaningful and where they come from.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.