Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden. It discloses the tool's output content (plan details, prices, features), states 'No arguments,' and hints at dependency on API key activation via register_free_key. While it doesn't explicitly say 'read-only' or list auth requirements, the behavior is clear: it simply displays pricing information without side effects.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.