When using the API Connector and making a call, you have 2 options to use for Use as - They are Data, and Action.
Data
Use as Data will allow you to use the action “Get data from external API” when setting a value. An example, using your API, is here:
Alternatively, you could use Use as Action.
Action
Action allows you to use the API as an independent action, which is what I believe your intent is. I also have an example here of that as well:
Conclusion
In conclusion, it all depends what you are trying to do with the API Call. If you are doing a POST, UPDATE, DELTE, or any action really other than GET, I would use it as an action. If the API call is a GET call, I would recommend using it as a Data call.
Let me know if you need more clarification,
Drake