Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false, but the description adds the details an agent actually needs before firing a destructive call: exactly what is destroyed (strip, description, voice binding), what survives (generations), and that the effect is permanent and irreversible. That is real added value beyond the structured hints.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.