Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the agent knows this is a non-destructive local mutation. The description adds the absolute-percentage framing but says nothing about out-of-range clamping, whether setting the volume also unmutes the microphone, or persistence across sessions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.