The paper introduces the Internet of Agents (IoA) architecture, which leverages interconnected AI agents for seamless discovery, communication, and collaborative reasoning. The architecture involves Wireless Agents (WAs) offloading compute-intensive tasks to Mobile Agents (MAs) or Fixed Agents (FAs). FAs can further offload tasks to Aerial Agents (AAs) using a two-tier optimization approach. The first tier uses a Stackelberg game for MAs and FAs to set resource prices and WAs to determine offloading ratios. The second tier employs a Double Dutch Auction for overloaded FAs to request resources from AAs. A diffusion-based Deep Reinforcement Learning algorithm is developed to solve the model, demonstrating superior task offloading performance.