Is the Oxford English Dictionary (OED) a descriptive dictionary?

The OED has been largely descriptive since its inception, although its usage notes have been happy to label certain usages as "incorrect". It documents through quotation how the meanings of words have developed over the years. That said, because of biases in the editorship towards literary sources, it hasn't always completely reflected the language in its earliest incarnations. With the digitization project that led up to the OED2, some of this was corrected but not all. Probably the best description is that it's descriptivist but with culturally conservative biases.