Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already cover the safe, read-only, idempotent nature of the tool. The description adds meaningful behavioral context by disclosing exactly what is returned (structure, not values or codes) and what the vintage represents. This goes beyond the annotations without contradicting them.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.