Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full behavioral burden. It adds valuable context by stating that the computation is local, involves no network call, and consumes no quota. It does not cover edge cases like empty input, but the '1+' constraint mitigates that concern.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.