Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate the tool is read-only (readOnlyHint, idempotent, non-destructive), which is the key safety trait. The description adds minimal extra value beyond that, as it doesn't detail what happens if no transition is set or whether settings might be empty. With annotations covering the safety profile, a 3 is appropriate for the modest additional context.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.