The developer APIs currently support a credit-based system. This credit-based system is used to pay for access to the developer APIs.
However, one question you might have is: Do I need to pay credits to execute a trade in the developer APIs?
The Shrimpy APIs do not charge for any trading endpoints. That means you can execute as many trades as you want without incurring any extra charges. Since the Shrimpy APIs charge for each user that is managed, we decided that all actions that can be taken on a user will be free. That means it's completely free to link exchange accounts to a user, free to trade, free to get balance data, and free to rebalance.
Notice: Trading still incurs exchange trading fees. Shrimpy does not pay the exchange fees for developers.