There are several ways to access DataRobot API documentation.
The current core API documentation can be accessed from the in-app Documentation resources (click ? at the top of the DataRobot UI), or from the customer support portal (accessible to DataRobot customers).
The DataRobot Support site provides a Readme with links to documentation and distributions, as well as instructions for installing DataRobot API clients. Again, the support site is available to licensed DataRobot customers only.
The R and Python modeling APIs are wrappers around the base REST requests.
The latest DataRobot R client, its documentation, and vignettes are all available on CRAN.
The latest DataRobot Python client is available on PyPI, and documentation can be found here. Examples of the DataRobot Python client being used to model airline and financial data are available here.