Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden. It does disclose persistence across runs and which fields are readable later, and it warns not to store secrets. However, it does not explain overwrite behavior, what the response is, whether data is private, or how long it persists.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.