I know it’s an old topic, but I’m adding a warning everywhere I see cd-discid mentionned.
It’s a pity because I really liked it, but this nice little tool should not be used for MusicBrainz, as cd-discid is affected by 3 bugs and it produces wrong data.
You should use a tool that uses the official libdiscid, like musicbrainz-isrcsubmit or MusicBrainz Picard tagger.