Can a shopping agent make an offer or reserve a car through OffLot's API?

No. The agent search at offlotai.com/api/agent/search is read-only, so it can't make offers, reservations or purchases. Offers are made by shoppers on the vehicle's final review page and require a free OffLot account. In the preview, reservations and real purchases are not live anyway. Agents should send people to the vehicle page to build a deal.