Redundant or Necessary? A Benchmark for Detecting Redundant Steps in Agent Trajectories

LLM-based agents have demonstrated strong capabilities in solving complex tasks through multi-step reasoning and tool use. However, existing evaluation protocols primarily focus on task success, overlooking a critical aspect of agent behavior: execution efficiency. In practice, agent trajectories often contain redundant steps that consume substantial resources while contributing little to task completion. In this work, we propose and formulate a new research area: redundant step detection for agent trajectories. To support this initiative, we introduce RedundancyBench, a new benchmark that contains diverse tasks with carefully annotated trajectories, where each step is labeled according to its contribution to task completion. Using RedundancyBench, we develop and evaluate 3 representative methods to answer whether a step within trajectory is redundant or necessary. Our results show that even the best-performing method achieves only 24.88% score in detecting redundant steps, while some methods perform worse than random guessing. These results highlight the task's complexity and the need for further research in this area. footnoteCode and dataset in this paper are both available in hrefhttps://anonymous.4open.science/r/RedundancyBenchhttps://anonymous.4open.science/r/RedundancyBench.