A small API balance top-up is useful, but it is not the end of onboarding.

For a developer tool, the next proof is one verified billable request: same project key, known model ID, expected cost visible, request log readable, and balance movement easy to explain.

Without that receipt, the user has paid but still has not learned whether the route is safe enough for real workload.

The receipt that matters

After the first top-up, the product should make the next request boring and auditable: