Is Your Agent Skill Actually Good? Microsoft's Dual-Paper Deep Dive into Skill Evaluation and Self-Evolving Optimization

The Question Nobody Wants to Ask: Does Your Skill Actually Help?

You spent an afternoon crafting a carefully structured Skill for your agent. Clear steps, thorough edge-case notes, well-formatted output requirements. You tested it manually a few times, the outputs looked great. You shipped it.

Three weeks later, you notice that some task success rates have gone down compared to before the Skill existed.

This is not a hypothetical. In May 2026, Microsoft Research published two concurrent papers — SkillLens ("From Raw Experience to Skill Consumption") and SkillOpt ("Executive Strategy for Self-Evolving Agent Skills") — that measured this failure mode at scale. Their finding: negative transfer happens in 25% of cases, and you cannot reliably identify the bad skills just by reading the text.

One paper answers "why skills sometimes backfire." The other answers "how to make skills systematically better." Together they sketch a new paradigm for agent capability improvement.