Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description fully discloses behavior: only longitude can exceed ±90, so certainty when values exceed that; otherwise returns 'inconclusive' without guessing. It also notes pure computation and no external API, plus the return format.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.