Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full transparency burden. It discloses the categories of data returned (hydrology, 30-year frequency, last five years' outcomes), which is helpful, but it does not mention whether the operation is read-only, any side effects, limitations, or data freshness.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.