Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true, which already tell the agent this is a safe, repeatable read operation. The description adds minimal behavioral context by specifying it's a GET request, but doesn't explain what validation entails, what happens on failure/success, or any side effects. With good annotation coverage, the bar is lower, but the description adds only basic HTTP method information.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.