Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already establish this as read-only, idempotent, and non-destructive. The description adds useful behavioral context by specifying what the report includes—number of regions, total monthly data points, latest month, and last refresh—and by scoping the data to Zillow Research ZHVI + ZORI at metro and state level.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.