[ISF]

You are putting 2 bets into what will usually be a 9sb pot hence getting 4.5:1 in a pot that is likely to be played aggressively. If you had pocked twos you could argue for a fold as just playing it for a set might be close to neutral ev, but 88 will win unimproved sometimes to so this is what makes it an easy call. A cap would be fine as well, but I would usually just call here with 88 and look for a favorable flop, maybe cap with 99.