You can find the swagger documentation on https://distribution.apaleo.com/swagger/index.html.
All apaleo APIs are described as Swagger documents. That lets you generate API clients directly from the swagger.json files. There is a large community, providing client generators for almost every language. For example, swagger code generator is a good project, which allows generation of API clients for Java, PHP, C#, NodeJS and more. This gets you up to speed very fast and as a bonus you can access API documentation within the auto-generated methods and models.