During the pre-release I ran into a question that I believe received the incorrect answer from people around me.
My opponent had a Mistcutter Hydra with three +1/+1 counters on it. My turn comes around and I attempt to play a Viper's Kiss. My thought is that since the Hydra has zero toughness, the Viper's Kiss would send the Mistcutter Hydra to the graveyard. My thinking was the enchantment would modify the toughness before the counters resolved. I did not call over a rules judge because we were already running long and I didn't really care enough about it at the time. I asked a few people around me and they said that the +1/+1 counters gave the Hydra that much toughness.
Now I'm very interested to know if I'm correct. I've looked through the rules and am unable to find a clear answer. Could someone please help me figure this out?
I know I should be able to figure this out by reading the rules and searching, but I haven't run across anything that gives me a definitive answer.
Edit: I can't seem to get Viper's Kiss to autocard. Here's the card text from Gatherer: