SF_13.3 - https://www.progress.com/documentation/sitefinity-cms/media-api/folders-operations

CreateAFolder.json

{
    "@odata.context": "http://mysite.com/api/default/$metadata#folders/$entity",
    "Id": "288eff11-6e67-48ae-aefc-45b1c97e898b",
    "LastModified": "2021-04-27T13:30:20Z",
    "UrlName": "86e4705e-3412-4558-a938-71b03e365992",
    "Title": "Folder title",
    "Description": "",
    "RootId": "d4e22033-7bcd-4ce5-9c70-41f9b83d7d66",
    "ParentId": null,
    "CoverId": null,
    "Provider": "OpenAccessDataProvider",
    "ChildrenCount": 0,
    "Breadcrumb": [
        {
            "Title": "New library",
            "FolderId": "477045b1-56f3-4abf-8799-33d42813636f"
        }
    ]
}