Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses the type of data returned (tokens, CSS variables export, component overrides) and notes the dependency on authentication. It doesn't mention side effects, but the read-only nature is implied by 'Returns,' and the description adds useful context beyond just the tool name.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.