Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral burden. It conveys that the operation is read-only ('List') and that the note count is dynamic ('live'), which is genuinely useful. It does not mention pagination or return formatting, but for a zero-parameter listing tool this is sufficient.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.