Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the burden of behavioral disclosure. It reveals a key domain rule (pieces in recently used domains will be held over), which is valuable context for acting on the results. However, it does not explicitly state whether the tool is read-only, nor does it describe the return format or pagination behavior. The disclosed rule is about the publishing system rather than the tool's execution, so it partially covers transparency.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.