Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false, covering safety and side-effect expectations. The description adds context about the data source ('official API') and the data structure (list with ID, name, star powers, gadgets), which helps set expectations about the response content. 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.