I'm going to double my tip by adding the cash tip to a credit card even though it was written in on the receipt
Isn't that stealing?
I'm going to brag about this tip size to my friends
So you're going to steal someone's money and then brag about it? You're either going to get fired or get in legal trouble. Do you think its worth it?
It's easy money and my life sucks without easy money.
Stealing from someone who was generous enough to leave you a tip is wrong and illegal. You might think its easy money now but if you lose a job and get labeled a thief you'll have a harder time earning money in the future.