The Regression Tax: Decomposing Why Skills Help and Hurt LLM Agents

Adding procedural skills to an LLM agent is typically evaluated by average improvement in task success.

Adding procedural skills to an LLM agent is typically evaluated by average improvement in task success. However, this metric hides an important cost: skills can also make agents worse. We measure both sides by comparing agents with and without skills across nearly 6,000 runs…