Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It accurately describes the primary behavior but discloses no edge cases: what happens if there is no forward history, whether it waits for page load, or what it returns. This is acceptable for a simple zero-parameter action but not deeply transparent.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.