Both above are correct. I assume you're having the carport poured and just want a higher level area for a tool shed? If so, they can frame that and fill it accordingly. Whether you pour concrete, or frame something with pressure treated lumber, I strongly suggest you consider making the finished floor inside the shed no higher than 10 inches above grade (of where you're stepping from). The reason is natural human comfort and coordination in taking a step up. This is even more true when carrying objects. 9 inches would be even better. As you go above 9, the human tendency is to catch a toe on the higher platform and stumble. There's a low number recommendation as well, but I don't recall it for sure. (It may be 6 inches - step elevations that are "too small" are also unnatural to our bodies.)
Also, if you fill and pour, be sure they compact the fill material so the floor slab won't be as prone to crack from fill settling. Also, insist on a vapor barrier for the slab portion where the shed will be.