SDK should have form of a single file class which can be included and used from some other project without additional external dependencies.
Constructor of class should have one parameter: API Key.
For each method of REST API must be defined equivalent method in SDK class.
Each class method must be named using snake_case convention.
Each class method must cover all REST method parameters and returning JSON deserialized object, method parameters must be aligned with documentation.
Along with a class file, there should be example file how to use class with few random examples.