Did you cook it covered or uncovered? What temperature? More likely than not you overcooked it or even cooked it at a temperature that was too high. One hour at the right temperature and covered shouldn't dry it out.
Yeah for breasts cut in half an hour is way too long. Plus if your baking chicken it's going to be pretty dry no matter what unless you cook it in something.
Next put your veggies and chicken in the pan, cover it with aluminium foil, and bake until your chicken's juice runs clear at 350 degrees. Poke it with a fork to find out. It should take 45 minutes or so. If you don't overcook chicken it won't be tough and dry.