Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden, and it implies a safe, non-mutating metadata read by describing only static descriptive fields. It does not disclose whether the dataset is versioned, whether the licence terms change, or whether the result can fail/stale-date, so gaps remain for a tool with zero annotation coverage.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.