Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of behavioral disclosure, and 'Process all pending files' communicates almost nothing about side effects. It doesn't disclose whether files are deleted, moved, or left in place after processing, whether the operation is long-running or asynchronous, how failures are handled, or what the return/outcome looks like. The only behavioral trait conveyed is the batch scope.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.