Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden. 'List files' clearly implies a read-only operation, and 'via FTPS' adds transport context. However, it does not explicitly state side effects, path handling behavior, or FTPS authentication/connection expectations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.