Notice how often you tell Claude the same thing? "Use our house style. Headline, then three bullets. British spelling. Sign off as the team, not me." Every time, from scratch. A Skill is how you stop repeating yourself. Teach Claude a job once, and it does that job your way every time.
What a Skill is
A Skill is a small package of instructions for one specific task. At its heart is a short file that says two things: what the task is, and how to do it, step by step. It can also carry extras the job needs: a template to fill, a checklist to follow, a bit of script to run.
The best way to picture it: a Skill is an onboarding note for a new hire, but for a single job. Not "here's everything about the company," just "here is exactly how we format a client report, every time." Hand that note over once, and the new hire never has to ask again.
Two kinds you'll meet
Ready-made Skills. Anthropic ships a set for everyday document work: Word, Excel, PowerPoint, and PDF. These switch on by themselves. Ask Claude to "build me a slide deck" and the PowerPoint Skill quietly does the heavy lifting. You have probably used one already without knowing its name.
Your own Skills. This is where it gets useful. You package a task you repeat: "format any report in our brand style," "turn my rough notes into our standard client update," "run this checklist over a draft contract." Once it is added, Claude reaches for it whenever a request fits.
The clever part: Skills stay cheap
Remember the context window from lesson 4.1, the desk that fills up? You would think a pile of Skills would clog it. They don't, and here is why.
Claude keeps only each Skill's name and one-line description in mind, a tiny cost, a handful of words each. It reads the full instructions only when a request actually matches. The rest of the time they sit on the shelf, costing almost nothing.
The upshot: you can build up a whole toolbox of Skills and pay almost nothing to keep them, because only the one you need ever opens.
You don't summon it, it shows up
Here is the part people find surprising. You do not call a Skill by name. You just describe the task in plain words, the way you always have. Claude reads your request, compares it to what each Skill says it is for, and reaches for the right one on its own.
That puts all the weight on one thing: the Skill's description. It has to say clearly what the Skill does and when to use it, because that description is the trigger. A vague description ("helps with documents") never fires at the right moment. A sharp one ("format a report in our brand style, use when the user asks for a report or a write-up") fires exactly when it should.
Where Skills earn their keep, and where they don't
Reach for a Skill when a task is repeatable and has a right way to do it. Formatting to your brand. A weekly report that always takes the same shape. A review checklist you run over every draft. Filling a form the same way each time. These are jobs where consistency is the whole point, and a Skill nails consistency.
Skip the Skill for one-offs and open exploration. Brainstorming, a single question, a first rough draft of something new: a plain prompt is faster and freer. Do not package a task you will do once.
A quick way to tell a Skill apart from things you already know. A prompt is a one-off instruction for right now. Your profile instructions (lesson 2.5) are broad background that colours every chat. A Skill sits in between and is sharper than both: a specific job, packaged, that fires by itself when it fits and can carry its own templates and steps, all without cluttering the window until it runs.
Making your own
You do not need to be technical. A Skill is really just a short text file, plus any templates you want it to use.
So the recipe is: write down the name, a crisp description (what plus when), and the steps in order. Add a template if the job needs one. Then, in claude.ai, upload it in your Settings (look under Capabilities), which works on the paid plans with file creation switched on. From then on, Claude uses it whenever a matching task comes up. One note for teams: a custom Skill you upload stays with your account, it is not shared across the whole organisation, so each colleague adds their own copy. The help-centre links below have the exact click-by-click steps.
One safety note
A Skill can tell Claude to run code and use tools, which is exactly what makes it powerful, and also what makes a bad one dangerous. So keep the habit from lesson 1.4: only use Skills you built yourself or got from a trusted source like Anthropic. If a Skill turns up from somewhere you do not know, treat it like software from a stranger: read it first, or leave it alone.
Where this goes next
A Skill is the how, a job done your way on demand. Next we cover the where. Projects (lesson 4.3) keep your files, your instructions, and all the related chats together in one place, so ongoing work has a home. Skills and Projects are a natural pair, and together they turn Claude from a clever stranger into a colleague who knows your work.
Try it
Write down three tasks you find yourself re-explaining to Claude, the ones where you always paste the same setup. Now pick the one with the clearest "right way" to do it.
Sketch its Skill in five lines: a name, a one-line description (what it does and when to use it), and three or four steps Claude should follow. You do not have to build it yet. Just seeing a real task from your week break cleanly into those parts is the point, that is the moment Skills stop being abstract.
(General exercise. Role and industry versions come once accounts are in.)