Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With only one parameter, no output schema, and no annotations, the description covers most of what an agent needs: what is created, who owns it, what comes back (checkout_url), and that the resource is not yet active. Missing pieces are auth/permission requirements and error behavior, which are minor given the tool's simplicity.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.