Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden. "Discard" hints at a destructive operation, but it never states whether the upload and its uploaded chunks are permanently removed, whether the action is reversible or resumable, whether special permissions are needed, or what error occurs for an invalid or already-finished upload.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.