Note that documents created from image files (TIFF, JPEG, JPEG2000) and PDFs that contain only images are automatically read (OCRed) before classification is performed. For small documents this will usually be very quick, but for very large documents you should expect response time to be up to tens of seconds.
The classification result contains several properties with different purposes. You should take care to understand these. The Classification results article explains all the properties and how to interpret them.
If you haven't added samples to the classifier
If you use a classifier before you have added samples to it you will get classification results where the document type and document type scores are
200 The Document was classified
400 No Document ID is specified or no Classifier name was specified
401 There is no Authorization header or the access token is invalid
404 The specified Document does not exist or the specified Classifier does not exist