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 does disclose the important toggle semantics (it turns the screen both on and off rather than a fixed direction). However, it omits device-state prerequisites, side effects, and whether it affects sleep/wake state beyond the screen.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.