Use "guest" credits even if not specified?

might be a bit self-explanatory, but if an artist—who isn’t/wasn’t a member of the band—is credited as doing vocals or instruments on a track, should they be credited with the “Guest” attribute even when it’s not mentioned in the booklet?

a hypothetical example, in a booklet you’ve got a list of say, band members X on guitar, Y on drums, and Z on bass, but artist G is credited as doing guitars on track 5. would artist G be credited as “Guest guitars” then?

moreover, I’ve seen a couple examples where some guests aren’t credited as “Guest” in a booklet, but others are. continuing the example above, artist S is credited as “Guest Synths” on track 3. should both G and S be credited as “Guest”, or just artist S?

one point, just for completeness’s sake, this probably shouldn’t apply when a band member left while recording an album. for example, artist L did guitars on tracks 2, 7, & 8 with X. they should probably not be credited as “Guest”, by any stretch.

No. Don’t use guest unless it’s that way in the booklet. It’s common mistake. Shouldn’t be used in place of featuring or any artist just because they may not be a member of the band. Credits should be credited as they are in the booklet. So, if the booklet doesn’t say guest, don’t use guest.