Daniel Larison has a nice write up on the subject.
I'd say the U.S. needs more politicians, especially Republican politicians, advocating for restraint abroad. That said, and with the caveat that I haven't followed the Paul campaign closely, is Paul the right vehicle for this message? On his Website he's called for the U.S. to pull out of the United Nations, the World Trade Organization and the IMF (but not Afghanistan). Imperfect institutions yes, but would this be any less radical and destabilizing than the interventionist policies pursued by previous administrations?
On his site Paul says he wants commercial engagement with the world - but the world, for better or worse, has built up a set of institutions to mediate commercial disputes and to conduct international economics along a rules-based system. You can, I suppose, junk it all and still trade with countries, but why is such a radical step needed? To protect U.S. sovereignty? Is it really threatened by the United Nations or WTO? Isn't the U.S. on surer footing when everyone acknowledges the rules of the road (even if they don't always play by them)?
It's one thing to make the case to the American public that U.S. foreign policy is too meddlesome in other states' business, too quick to reach for punitive sticks and too grandiose in scope and ambition. If that was Paul's message, I suspect it would find a lot of takers. But this is only a piece of what is a larger, more radical frontal assault against the post WWII institutions that, for better or for worse, the U.S. has worked to shape and lead to our general betterment. Some, like NATO, have arguably outlived their usefulness. Others, like the IMF and World Bank, likely need reforms. But a blanket rejection of U.S. participation in all of them just seems ill considered.
Having a voice of restraint in the Senate would certainly be a good thing and I'd be hard pressed to argue against anything Paul elucidates in the video below. But I would suggest that there's more to restraint than avoiding unnecessary wars - like not seeking a wholesale and radical revision of the international order.