Q: I'm getting a "DESCRIPTION_DATABASE_DOES_NOT_EXIST" / "DESCRIPTION_INVALID_DATABASE" error!
A: This shouldn't happen any more, as FBI takes care of initializing the database files for you. However, if it does, you likely haven't installed anything from eShop or other locations before. You will need to go to the "Nintendo 3DS/<id0>/<id1>/dbs/" directory on your SD card and create empty "title.db" and "import.db" files. Then, go to System Settings -> Data Management -> Nintendo 3DS -> Software on your 3DS and let it repair the database files.