Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries full burden. It discloses the full user flow (user opens URL, connects wallet, pays $15 USDC), states the session is created, names return values (payment URL and price), and clarifies the tool call itself is free. This is rich behavioral context.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.