Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It transparently discloses the core operation (an outbound fetch of a public file, read-only, no auth implied) and the reduced result shape. But it does not disclose failure modes (e.g., missing robots.txt, redirects) or define what 'group counts' means.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.