Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds a catalog of valid skill names but little about operational behavior, such as defaulting to SKILL.md, using '.' to list roots, or how output is structured (though some of that is in the schema). No contradiction with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.