The Cycle API is a REST-based, resource-oriented API designed to be easy to use and understand. Using this API, you are able to fully interact with the Cycle Platform. In fact, this is the same API used by our Portal.
All API responses return JSON, including errors. There is also support for cross-origin resource sharing, so this API can be used in a client-side web application as well.
In addition to the standard REST API, there is another websocket-based API, called the Notification Pipeline, that you can tune in to for streaming updates of platform resources.
We've released an official NodeJS (Typescript) library, with Go support on the way.