Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does disclose the return encoding and format (base64-encoded ZIP containing CSVs), which is genuinely useful and non-obvious. It says nothing about permissions required, export size limits, whether the ZIP is a synchronous snapshot, or how pagination affects the exported dataset, which are material for a potentially expensive bulk operation.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.