Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations at all, the description carries the full behavioral burden but supplies almost nothing: no statement that it is a read-only operation, no pagination or result-cap behavior, no behavior on an unknown pool (empty list vs error). Only the word 'indexed' hints that results are limited to already-ingested repos.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.