Your question is Design External Partner API Approach. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
You're defining an API that external partners will integrate with to access a payments capability. Because outside teams will build against it, the API design has to balance ease of integration with security, reliability, supportability, and long-term versioning.
What factors do you consider when creating an API for external partners?