Which API to Use?

Content

I am gathering requirements for an in-app form (and later, an SDK) to be built, which would gather customer information and pass-through data which would create an incident. We will map to both system and custom fields. We did something similar, years back, and used (what was then just referred to as) just RightNow Connect. Now, we have several APIs to choose from. I will be working with an engineer here to integrate, and they will be unfamiliar with RightNow, so I want to make sure to provide them with the most effective documentation.

Has anyone done something like this, and which API do you suggest for this purpose?