Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide no behavioral hints, so the description carries the full burden. It communicates that the operation appends data and requires an active import, but it does not explain ordering, idempotency, effects of invalid uploadId, failure behavior, or what happens after the final part is appended.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.