Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It openly discloses the statistical methods (t-based and Wilson), the two input modes (data vs. summary statistics), and the default confidence level (0.95). It stops short of describing edge cases, error behavior, or assumptions like normality, but the core behavioral choices are transparent.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.