Agent Skills - A Comprehensive Primer

This is the full primer behind my Agent Skills masterclass, a practical, no-fluff reference for building, evaluating, and shipping skills across Claude Code, ChatGPT and Gemini.

You'll get the open Agent Skills standard and SKILL.md file format; a clear mental model for skills vs. MCP vs. subagents vs. plugins; platform-by-platform breakdowns for Claude Code, Codex CLI, and Gemini CLI, including their extended frontmatter and quirks; a full workflow for designing a new skill from scratch, sourcing real expertise, and avoiding the generic-instructions trap; techniques for writing descriptions that trigger reliably instead of silently failing; an eval-driven development framework for testing and scoring skills before you ship them; and a walkthrough of the Karpathy-style "autoresearch" loop for autonomously improving a skill overnight.

23 pages, written for anyone (technical or non-technical) building or maintaining agent skills.

Want to go deeper? This primer is a companion to my live Agent Skills masterclass here on Maven.