Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide strong behavioral hints (readOnlyHint: true, destructiveHint: false, idempotentHint: true, openWorldHint: false), indicating a safe, non-destructive, and deterministic operation. The description adds value by specifying the return details ('Current login status and whether a cookie is available'), which isn't covered by annotations. No contradiction with annotations is present.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.