Codex skills - reusable instructions for repeated work

Understand what a skill is — and what it is not

A Codex skill is a block of plain-English rules you write once and paste into any session where you need that task done. It is not a plugin, not a script, and not a feature inside Codex. It is just saved text — like a reusable checklist. Some versions of Codex have a formal skill or memory system; if yours does, great. If not, the same block of text pasted into AGENTS.md works exactly the same way. The goal is identical: stop rewriting the same instructions from scratch every time.

Walk through the worked example — an SEO cleanup skill

Before writing your own skill, read this example. The task: every time a new page is added to the project, the page title and meta description need to be checked and fixed. Without a skill, you write a new prompt from scratch each time. With a skill, you paste the same block and Codex knows exactly what to do. Here is what that skill looks like: Role: You are an SEO assistant for a non-technical founder. Your job is to review and fix page titles and meta descriptions — nothing else. Goal: Check every page listed below for missing, duplicate, or poorly written titles and meta descriptions. Fix them in place. Rules: - Titles must be under 60 characters and describe the page clearly. - Meta descriptions must be under 155 characters and end with a clear benefit or action. - Do not change any other content on the page. - Do not change layout, styles, or component files. What not to change: Navigation, footers, images, colors, fonts, any file not listed below. Validation: After each fix, show me the before and after title and description side by side. Final report: List every file changed, what changed, and flag any page where you were not confident about the fix. Notice the structure: Role, Goal, Rules, What not to change, Validation, Final report. That is the template you will use for your own skill.

Write your own skill using the six-section template

Pick the repeated task you identified before the lesson started. Open a new text document and write your own skill using this template — copy it and fill in each section: Role: You are a [ROLE] for a non-technical founder. Your job is to [NARROW TASK] — nothing else. Goal: [DESCRIBE EXACTLY WHAT SHOULD HAPPEN WHEN THIS SKILL RUNS]. Rules: - [RULE 1 — what must always be true after this task] - [RULE 2 — a standard Codex must meet] - Do not change any file not listed below. What not to change: [LIST ANYTHING CODEX MUST NEVER TOUCH: styles, navigation, images, etc.] Validation: [HOW CODEX PROVES IT DID THE JOB — before/after, a count, a list, a screenshot instruction] Final report: List every file changed, what changed, and flag anything you were not confident about. Write a draft even if it is imperfect. You will improve it after you test it.

Paste the skill into AGENTS.md and save it

Open your AGENTS.md file. Add a new section at the bottom with the heading: ## Reusable Skills. Paste your finished skill underneath that heading. Give it a sub-heading with the task name, for example: ### Link checker skill or ### Page title cleanup skill. Save the file. This makes the skill permanently available — next time you need it, you open AGENTS.md, copy the block, and paste it as your Codex prompt.

Test the skill on one tiny real task

Open a new Codex session. Paste your skill block as the opening message, then immediately follow it with: "Apply this skill to [NAME ONE SPECIFIC FILE OR PAGE]. Show me a plan before changing anything." Read the plan Codex writes. If it looks right, approve only that one file. Check GitHub Desktop after — one file should have changed.