Fortellis APIs are grouped by their domain in the automotive business. Domains cover front office functions (Sales) to fixed ops (Service).
The domains available can be seen on the left navigation split into different sections. Under each domain there are links to the available APIs under that domain. This is a great place to start browsing for APIs to use in your solution.
Each API has its own page with a list of all the methods for the API. This page serves two purposes. It gives you a more detailed look at what you can do with the API, and it is how you access detailed information for the API endpoints.
Each name in the endpoint list opens to display more information.
On each API page, clicking on an endpoint will provide more details. Most of the information comes directly from the API spec. Look here for:
Navigate to the first API here or choose one from the left to start exploring.