You can retrieve (the configuration of) a specific class/documentType to confirm it exists or to parse something from its metadata if you have its documentTypeId (class ID).
documentType is the APIv1 is the API versionlibraries is the top-level resourcedocumentTypes or class is the nested resourcedocumentTypeId) and the library ID (libId) of the library the class resides in — both as path parameters (not in the query string).
id (of the class)displayName (of the class)libraryId (of the library you searched)defaultClass (whether or not this is the library’s default class)