I think you know how to do this. You are head of engineering at an AI startup. You know how to create and revoke API keys and how to share them with your interview candidates.
1. Whatever limit I put needs to be completely arbitrary. 5$? 10$? 2. I cannot guarantee they will use it correctly. They might use it for the challenge. They might use it to generate harmful content. 3. It requires me to manually create and revoke keys. Candidates might want more credits. They might get leaked.
There are solutions. I just can't think of good ones.