Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already provide readOnlyHint, idempotentHint, openWorldHint. The description adds specifics: matches on name/tagline/category, case-insensitive substring, returns up to 20 results, and only searches live, published tools. This goes beyond annotations and clarifies behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.