Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. 'List' implies read-only, but nothing is said about whether results depend on a prior scan being run, the scope of analysis, or cost/latency for a whole-repository sweep. These are exactly the traits an agent needs before invoking it.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.