Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations present, the description must carry the behavioral burden, but it only states the action. It does not disclose whether the original asset is modified or a new asset is produced, whether rendering is triggered, or whether the operation is destructive/reversible.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.