Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false. The description adds behavioral context beyond those: it explicitly states the tool performs a login to the official backend and returns the session token, branches, and user data. This clarifies the nature of the operation (a validation, not a persistent connection) and what the response contains, complementing the annotations without contradiction.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.