A Comprehensive Review of AI Agents: Transforming Possibilities in Technology and Beyond

The development of artificial intelligence (AI) agents--autonomous systems capable of perceiving their surroundings, reasoning about possible courses of action, and executing decisions--has evolved significantly in recent decades. Early AI agents, rooted in the symbolic reasoning systems of the 1950s and 1960s, relied on hand-crafted rules and logic-based methods, excelling in constrained domains but struggling with adaptability and uncertainty[1, 2]. The introduction of statistical learning and probabilistic reasoning in the 1980s and 1990s enhanced reliability, while the rise of reinforcement learning (RL) allowed agents to learn policies through trial-and-error interactions [3, 4, 5, 6]. The integration of deep neural networks with RL (DeepRL) led to breakthroughs such as superhuman performance in Atari games and Go [7, 8]. With growing computational power, recent advancements in statistical methods and machine learning, AI agents have incorporated advanced perception, natural language sequence modeling, and cognitive-inspired principles, enabling them to adapt, collaborate, and mirror aspects of human reasoning in dynamic environments [2, 9, 10, 11, 12, 13, 14]. Contemporary AI agents are increasingly deployed in high-stakes, real-world contexts: self-driving cars navigating congested urban environments [15, 16], autonomous laboratories accelerating scientific discovery [17, 18], virtual assistants managing complex user queries [19], and automated trading agents operating in financial markets [20].