Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses the conversion behavior, the output format (JSON with shapefile_zip_base64 and warnings), and implies a safe, non-destructive operation. It could mention limitations or size constraints, but the return structure and warnings add useful behavioral transparency.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.