You should rely on the guide to have (or have access to) all the technical gear needed. If he doesn't, how could he possibly have learned his trade? To put it another way: a guide that doesn't have the right tools I would not trust with my life!
As for non-technical stuff, it might be a good idea to bring your own tent, assuming you have a good one. Otherwise you may have to pay extra to rent one, and you might not be able to find one as good as yours. Likewise, If you have a stove that works fine at altitude (ie, well above 5000m), by all means bring it along.
From your description, I can't clearly determine if you are going to hire a guide for just yourself, or a larger party. For technical routes, no respectable guide should take more than two clients on his rope; for difficult ones just one. As an example, in 2011 the conditions on the route where such that I would not want to go with a guide that would be willing to take three clients on Huascarán.
Mind you, I see how this could pose a bit of a problem: if you are looking for a guide to climb a route, you do not yet know its current condition; once you've climbed it, you don't need a guide anymore. So, ask around about route conditions.
Your post does not mention hiring other people, such as porters or a cook. More people obviously require more than one tent (or a bigger one). In the Cordillera Blanca, I climbed with people that I met locally or via SP, and I soloed some routes, but on one occasion I used an agency to hire a guide and a porter just for myself. I brought my own tent, they got one from the agency. I don't remember if I had to pay extra for it, but I wouldn't be surprised. However, I do remember that the guide wasn't very happy with their tent. They had a lot of condensation inside. The agency also provided a stove, for which I paid a small fee, and that worked just fine.