Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations present, the description must carry the behavioral disclosure burden, but it only states the core split operation and one negative guarantee. It does not disclose how a URL vs hostname is treated, what the output structure is, whether any network access occurs, or how invalid or empty input is handled, so an agent cannot predict runtime behavior.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.