What is a Claude Skill?

It’s Friday, 4pm.

You are sneakily writing in the group chat about tonights plans, whilst mentally wrapping up that one final task you have to do before the weekend.

Freedom is near.

Then… your boss pings you.

“Heyy, sorry to be a pain but can you make me another quick PowerPoint slide? Just like that one you did for Amy last week but this time, about all the AI projects we definitely are doing? And for Monday?? You’re the best <3”

Weekend ruined.

You have a few options now of how you complete this task:

Ahhh the point emerges.

This (true) anectode was just to show you that Skills are useful little buggers. Unlike quite a lot of AI-tools I have come across, Skills are something that you will actually use and probably will save you a lot of time.

So, now that I have whipped up your interest - hopefully - let’s dive straight in with:

A Skill is a reusable set of instructions stored in a file that you can give to Claude so it can perform specific tasks more efficiently and more consistently.

Perhaps you have already experienced the feeling of typing a prompt over and over again, into Gemini, ChatGPT or Claude.

A Skill saves these instructions so that you can use them again in the future, without the need to type it out each time from scratch.

Like the example from above.

Imagine you already invested a bit of time writing the perfect prompt for creating PowerPoints exactly the way your fussy boss likes them.

Well, with a Skill you can save these specific instructions and use them another time.

We will look at how Skills are written in just a bit.

The most important question… why should I care?

You should care because Skills let you do stuff faster, better and with less stress.

A good rule of thumb is, if you have a task which is:

Then you can probably write a Skill that can automate at least a big chunk of this task.

Take our example:

Without using a Skill, each time you want to create a PowerPoint using Claude, you will need to type the same context over and over again.

"Write in my voice. Use British English. Follow this structure. Save it here."

With a Skill, you save yourself all of the bother and just tell Claude “run skill presentation-builder for my slides on what-is-a-skill” and it knows exactly how you want this task to be performed.

For me, the first Skill I tried to build was a “notes-fact-checker”.

This is a task I found myself doing again and again.

I would write notes about a new AI topic by hand, then copy and paste these notes into Claude and ask it to fact check, tell me anything I might have missed and generally help sharpen up my knowledge.

I was doing this again and again and again.

Sometimes I would forget to ask for missing information or it might get too cocky and start rewriting my notes even though I didn’t ask it to.

So instead, I built a Skill called “blog-fact-checker”.

In this Skill I wrote exactly what I wanted Claude to do (fact check) and exactly what I didn’t want Claude to do (don’t be cocky)

I can honestly say (since I am not getting paid by Claude sadly), that this has genuinely saved me time and effort.

Before we look more closely at a Skill in detail, you should know that there are roughly two types of Skill:

These are skills that Anthropic provides automatically in Claude.

You don’t need to write the Skill yourself and actually they run automatically when Claude thinks you will need them.

Keep your eye out and you will also start to see different Skills running automatically in the background of Claude!

For example, when you ask for a pdf file, Claude runs a Skill which automatically generates the pdf as a downloadable document instead of just giving you text to copy.

Here are a couple of examples of the publicly available Skills from Claude:

These are the interesting ones!

These are Skills you build yourself for your own specific needs. Your brand guidelines. Your workflows. Your preferred output format.

The tasks that are specific to you that Claude has no way of knowing about unless you tell it.

This is where it gets powerful. A custom Skill can be as simple as "always format emails this way" or as complex as a multi-step workflow that searches databases, fact checks content, and saves output to specific places.

A Skill itself is just text that lives in a markdown file called SKILL.md.

Within this file is all of the information that Claude needs to understand:

You can also include other resources along with this file, which might help Claude perform the task.

For example, you could add some branding examples, blog styles to follow…anything that might help the model understand better.

I have written whole post on “How To Create a Skill”, because there is a lot that can be said about this topic.

For now, it’s just good to know that a Skill is a set of instructions stored in a simple Markdown file.

There are a couple of places you can store this newly written Skill so that Claude can access it.

One approach is a GitHub repository.

You create a repo, add a folder for each Skill, put the SKILL.md inside it, and store your example files and reference documents alongside it.

One repo for all your Skills, neat folders for each one.

Then Claude can fetch the raw file URL directly whenever you need to run this Skill

You can also store Skills in a Claude Project by uploading the files directly — no GitHub required.

The GitHub approach is best if you want version control, or if you might want to share your Skills with other people one day.

As my vibe-coding husband will happily confirm…no.

Not for simple Skills.

Writing a SKILL.md is just writing in plain English inside a markdown file, zero coding required.

You can even get an AI Model to help write the Skill for you.

In fact, Claude even has a SKILL for writing SKILLS. Yep.

More complex Skills can include executable scripts, Python or Bash files that Claude can run as part of the workflow.

But that is firmly in advanced territory and you do not need it to get started.

The most important bits from this post: