SWE-Skills-Bench tested 98 public agent skills across 3,920 paired evaluations and found 92 of them had no statistically significant effect
AspireAI community · arXiv (ControllableModel and collaborators)
*Agent skills - structured procedural packages injected at inference time - are widely installed on the assumption they make coding agents better, but no standard procedure tests an individual skill before you install it.* swe-skills-bench starts from 98 public SWE skills, each paired with a real GitHub repository pinned at a fixed commit, derives repository-specific requirements with executable verifiers, and runs every task once without the skill and once with it under four agent-model configurations, giving 3,920 paired evaluations. Each skill's deltas are aggregated into a utility profile and classified by a statistical test as Golden, Ineffective or Harmful.
The result is mostly negative: 92 of 98 skills show no statistically significant effect, and adding skills moves the average pass ratio only from 76.6 percent to 76.9 percent. The few that help supply procedures the agent would otherwise have skipped, with gains up to +17.7 points. The few that hurt anchor the agent on their own templates and override the task's explicit instructions, costing up to -17.0 points. The benchmark ships as code, so a skill can be tested before it is trusted.
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