Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden. It usefully discloses an output interpretation ("matched_agent — false means the key has no indexed activity"), which is valuable given there is no output schema. However, it omits auth requirements, cost/compute expectations, and time-window behavior for a metrics tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.