Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden, and it does disclose valuable behavior: result validation and automatic fallback to a second free provider. However, it omits cost/permission implications, what triggers a fallback, and whether the provider choice is honored or overridden.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.