Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare the safety profile (readOnlyHint=false, idempotentHint=true, destructiveHint=false, openWorldHint=true), so the description is not required to carry that burden. It still contributes nothing beyond them: no mention of what fields are replaced versus left untouched, whether omitted fields are nulled, or whether permissions are required for a mutation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.