DRIVERS-2577 : Drivers must sync the new runCommand unified spec tests: specifications@ab66eaf , specifications@146964a , and specifications@d697477 Drivers should make note of RunCommand implementation details  which requires drivers do not inspect nor modify the user's command document. If your driver does modify user input, file a follow up ticket tracking changing that as a future improvement. Add salient documentation for: A driver MUST not inspect the user's command, this includes checking for the fields a driver MUST attach to the command sent as described below. Depending on a driver's BSON implementation this can result in these fields being overwritten or duplicated, a driver SHOULD document that using these fields has undefined behavior.