Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With destructiveHint=true already signaled, the description goes well beyond the annotation: upsert key on (project, sourceTerm, source, target), staleness marking of matching TM entries, whitespace trimming, rejection of empty source terms, and the doNotTranslate override that forces targetTerm = sourceTerm. These are exactly the destructive side effects an agent needs to know.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.