Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It does disclose that the selected theme becomes the active theme, implying the previous theme is no longer active. However, it does not mention side effects (e.g., whether the old theme remains installed), potential failure conditions, or permission requirements. The core behavior is clear, but additional context is absent.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.