{"slug": "build-a-custom-ai-skill-in-37-lines-with-working-code", "title": "Build a Custom AI Skill in 37 Lines (with working code)", "summary": "A custom AI skill can be built in 37 lines of code, according to a developer guide. The skill reviews a git diff and returns a structured critique covering bugs, security, style, and performance, formatted for PR comments. The author argues that such skills encode team-specific rules, like banning console.log in production, making AI assistants more tailored to a codebase.", "body_md": "Member-only story\n\n# Build a Custom AI Skill in 37 Lines (with working code)\n\nMost teams I work with have already adopted an AI coding assistant. Few of them have taught it anything specific to their codebase. That is the gap custom skills fill.\n\nA skill is a small, named bundle of instructions, usually 20 to 40 lines, that an AI agent loads on demand. It does not sit in the system prompt burning tokens. It lives in a folder, has a name, and gets invoked when the task matches.\n\nIn this post we will build one. The whole thing: 30 lines, two files, one bash command to install. The skill reviews a `git diff`\n\nand returns a structured critique covering bugs, security, style, and performance. The output is formatted so you can paste it straight into a PR comment.\n\nBy the end, you will have a working pattern. I will give you three more skill ideas at the bottom that you can ship in an afternoon each.\n\n*By the way, if you are not Medium member, please click **here** to read.*\n\nWhy this matters: a vanilla AI assistant knows JavaScript. It does not know your team’s rule against console.log in production. A skill encodes that rule once, and every future session follows it. That is the difference between an assistant you use and an assistant that fits.", "url": "https://wpnews.pro/news/build-a-custom-ai-skill-in-37-lines-with-working-code", "canonical_source": "https://blog.stackademic.com/build-a-custom-ai-skill-in-37-lines-with-working-code-0c7a699f512a?source=rss----d1baaa8417a4---4", "published_at": "2026-07-22 07:41:11+00:00", "updated_at": "2026-07-22 07:56:21.529384+00:00", "lang": "en", "topics": ["artificial-intelligence", "ai-agents", "developer-tools"], "entities": [], "alternates": {"html": "https://wpnews.pro/news/build-a-custom-ai-skill-in-37-lines-with-working-code", "markdown": "https://wpnews.pro/news/build-a-custom-ai-skill-in-37-lines-with-working-code.md", "text": "https://wpnews.pro/news/build-a-custom-ai-skill-in-37-lines-with-working-code.txt", "jsonld": "https://wpnews.pro/news/build-a-custom-ai-skill-in-37-lines-with-working-code.jsonld"}}