Last week I read a paper that made me re-evaluate everything I have written about AI agent optimization. Microsoft and three Chinese universities published a method called SkillOpt. The result: a single Markdown file, between 300 and 2,000 tokens, lifted GPT-5.5 by an average of 23 points across six procedural benchmarks. No fine-tuning. No new model. No extra tools. Just a Markdown file that gets fed to the agent as context at inference time.
The skill beats handwritten instructions, one-shot LLM-generated instructions, and four specialized training methods (Trace2Skill, TextGrad, GEPA, EvoSkill). It works in Codex. It works in Claude Code. It transfers across model sizes. A spreadsheet skill trained in the Codex loop lifts Claude Code to the same level as a skill trained directly in Claude Code.
After reading the paper, I stopped adding features to my AI agent for a week. I started writing skill files instead. Five of them. All under 1,000 tokens. All producing measurable improvements in my daily work. This post is the five skills and the pattern I now use by default for any procedural task.