Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden, and it says nothing beyond the literal action. It does not disclose whether the call blocks until load completes, how it interacts with in-flight navigation, or that a normal reload may serve cached content (the cache nuance lives only in the schema).
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.