Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and a closed world, so the safety profile is fully covered without the description. The description adds the shape of what comes back (status, layout, content, trigger, targeting), which is useful, but says nothing about failure behavior for an unknown id or whether the returned data is live or cached.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.