Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full burden. It only states 'List files' with no disclosure of requiring authentication, pagination behavior, or what data is returned for each file. It does not contradict annotations since none exist, but it is minimally informative.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.