Isn't This Just a Clever Tautology?

According to saint anselm and descartes, it's believed that you can prove the existence of god simply by forcing your thoughts about him to essentially bite their own tails. So so how isn't this just a clever tautology, analogous to the ontological argument proving the existence of God? Youknow, it could be used to prove theexistence of anything. What you're saying here doesn't have the same structure.