I have seen the documentation for the Access API -- both the web pages at http://developer.crownpeak.com/Documentation/AccessAPI/index.html and Swagger. Unfortunately, there are times where I am left guessing the meaning of a particular parameter and/or what are acceptable values for a parameter. For example, the /accessapi/asset/create method has many parameters whose datatype is an integer. The range of acceptable values and specific meaning of those values isn't documented.
As an aside, the V3 interface uses the Access API so anything you can do in V3, you can do through the Access API. Knowing this, you can do a little investigation into the API parameter values by using an intercepting proxy, Charles is a popular choice but I prefer MITMProxy, between the browser and the CMS backend.
This method won't tell you what the range of accepted values is for each parameter, but it is a good fallback while the Access API documentation is brought up to speed.