Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full burden. It discloses that changes in amount, fact, rule step, or source digest cause failure, providing some behavioral insight. However, it does not mention return format, side effects, or whether it is idempotent. The output schema likely covers some of this, but description itself is moderately transparent.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.