Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description must disclose side effects and operational behavior, but it only states the transformation at a high level. It does not say whether it fetches responses via api_key, writes files into the directory, or what output it produces, so an agent cannot anticipate the tool's full effect.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.