Write it once: your first AI skill

Updated 26 October 2026

The short answer

A skill is a folder holding one instruction file, called SKILL.md, plus any examples, that teaches an AI one job your way: your email tone, your report layout, your job-advert style. You write it once, and the AI uses it whenever a request matches, instead of you pasting the same prompt every time. Claude and Gemini both let you upload a skill today, and the format is an open standard, but each tool handles skills a little differently, so test yours in every tool you use.

Why it is worth fixing

Retyping the same instructions takes time, and everyone types them a little differently, so the output drifts. A skill keeps the instructions in one place, so the whole team gets the same house style.

The format is now shared. Anthropic, which developed it, has handed the Agent Skills standard to the Agentic AI Foundation under the Linux Foundation, and says dozens of agent platforms have added it, including ChatGPT, Cursor, GitHub Copilot and VS Code. Google says skills will soon replace Gems in Gemini, and OpenAI plans to retire custom GPTs, turning each one’s instructions into a skill inside a plugin. Added doesn’t mean identical, which is why testing matters.

Step by step

  1. Pick one job you explain over and over

    Good first skills are small and specific: how you write a candidate summary for a client, your job-advert layout, the tone of your follow-up emails. Anthropic’s advice is to keep each skill focused, so make separate skills for separate jobs rather than one skill for everything.

  2. Make the folder and the file

    Create a folder named in lower case with hyphens, such as house-style, and inside it a plain text file called SKILL.md. The file opens with a short header between two lines of three dashes, holding a name and a description. The specification says the name must match the folder name, and Gemini also expects lower case with hyphens, so this works in both.

  3. Fill in the blanks

    In the header, write name: house-style, and a description such as: Use when writing emails, job adverts or candidate summaries for [your agency]. Below the header, write the instructions. Tone: [friendly and direct]. Layout: [the answer first, short paragraphs, one question at the end]. Always: [UK spelling, sign off with a first name]. Never: [the words and phrases you dislike]. Then add a good example.

  4. Write the description with care

    The description is what the AI reads to decide when to use the skill, so say what it does and when to use it. Claude’s help pages say to try several requests that should trigger it, and to rework the description if the skill isn’t used when expected.

  5. Add one example of the real thing

    Paste in an email, advert or summary you are proud of, with names and personal details removed. Both Anthropic and Google advise including examples of the output you expect, because an example shows the AI what good looks like better than a description can.

  6. Test the same skill in two tools

    In Claude, open Customize, then Skills, and upload the folder as a ZIP file; Anthropic says this works on the Free, Pro and Max plans as well as Team and Enterprise. In Gemini, open Customize, then Skills, and upload the SKILL.md file; Google says uploading works on the web and in the Mac app, for personal accounts of people over eighteen for now. Give both the same requests and compare the results with your example.

  7. Keep one master copy

    Keep the folder in one shared place, change it there, and upload it again to each tool when it changes. Read any skill from someone else before you switch it on: Claude’s help pages advise reviewing a skill’s files first, even one shared by a colleague.

Checklist

When it is worth getting help

A house-style skill is a good one to write yourself. It is worth getting help when you want a skill to work with your own systems, such as pulling a candidate’s details from your CRM before writing, or when a team needs the same skills set up and kept current across several tools.

Rec Int. builds AI automation for UK recruitment agencies, around the systems they already run.

Questions people ask

Is a skill the same as a custom GPT or a Gem?

They do a similar job: saved instructions for a task. Google says skills will soon replace Gems, and OpenAI plans to retire custom GPTs and move their instructions into skills inside plugins. Check the notice on your own account for the timing.

Which plans let me upload a skill?

In Claude, every plan, including Free, though a Team or Enterprise owner can switch skill uploads off. In Gemini, personal accounts of people over eighteen, with work and school accounts to follow. In ChatGPT, OpenAI says personal skills are generally available on Business, Enterprise, Healthcare and Edu plans.

Sources

If you would like to talk through skills that work with your own systems, book a discovery call.