SDKs
There is no SDK yet. The API is small — about twenty operations — and still a draft, and no SDK generator signs requests our way, so a generated SDK would be hand-written code that breaks more easily.
Instead, each language has a signing module of a few dozen lines and an example for every operation, all run against the sandbox on every release. Copy the module into your project and call the API with your usual HTTP client.
We will publish SDKs when the API is approved as stable, or when merchants ask for them. Tell your account manager which language you need.