Developers new to the Design Automation API are sometimes confused about how to use the various product API's with this technology.
The above diagram is just a high level view of how this technology works, but should be useful to clarify where exactly the various API's are being used.
As you can see, in order to take advantage of this API you only have to call its RESTful endpoints, and the various product API's (like Inventor API) is only used on our servers (shown as "My Code" in the above diagram) and is not something that you would be using directly from your client application (web service, mobile app, etc)