Thanks! If I can recall correctly, MBz API doesn’t inform UPC numbers - something essential to the Spotify integration. But it seems nice and I’ll study it further.
Hi! MusicBrainz team member here. We do have UPC numbers (well, barcodes), although if it was me doing this I would depend on those as a second source, and first check if there's an actual Spotify album ID (which we already store, but we don't have that many of right now). In fact, this seems like the kind of app that might make people actually go and add more Spotify album IDs in MusicBrainz just to get more/better content in Concertmaster.