The Recommendations APIs enable you to programmatically interact with Target’s recommendations servers. These APIs can be integrated with a range of application stacks to perform functions that you would typically do via the user interface.
Resources (e.g. Collections, designs, criteria) that are created in the Recommendations classic UI are currently not returned by the APIs. Any resource that is referenced by another resource, for example a design that is referenced by a recommendation, cannot be deleted until all of the references have also been deleted or the reference removed.
I believe this article in the Adobe.io documentation on Recommendations APIs is what you're looking for, but feel free to reach out here if you have additional questions. Hope this is helpful!