Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of disclosing behavioral traits. It states 'compress all images' implies a mutating, site-wide operation, but does not clarify whether originals are overwritten, whether it is reversible, or whether it may take a long time or require special permissions. This lacks necessary context for a potentially destructive bulk action.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.