Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=false, destructiveHint=false and openWorldHint=false, so the safety envelope is already given. The description adds genuinely new behavioral context by clarifying the operation copies rather than moves, meaning the source file survives — something the annotations do not express. It still omits overwrite/collision and destination behavior, so not a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.