Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full behavioral burden, yet it discloses nothing beyond the basic operation: no auth requirements, no behavior when the id is unknown, and no indication of what the returned order contains. A read-only nature is only implied by the verb 'Get'.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.