Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden. It adds the output unit ('metres') and tier availability, which are useful. However, it does not disclose potential errors, coordinate bounds, or data source details, which would be expected for a tool with no annotation support.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.