Yes. Your cashu token is your API key. They are interchangeable.

If you started a session with a cashu token, that cashu token becomes your primary API key. Even if you top-up the balance of this original cashu token, it'll still remain your API key with balance, the cashu token you used to top up will be spent and useless.

You can of course get a smaller API key using your original cashu token as well. (like sk-asdfasd)