For regular Claude.ai users. No tech skills needed. This shows you exactly how to build a Skill, what to write, and how to make Claude use it automatically every time.
A guide by Mariah BrunnerWhat is a Skill?
A Skill is a set of instructions you write once and save to Claude. After that, Claude knows your workflow automatically — no copy-pasting the same prompt, no re-explaining your preferences in every new chat.
Think of it like training a new hire. Instead of re-explaining the job every day, you hand them an onboarding guide. Skills are that guide — but for Claude.
A guide by Mariah BrunnerYour Skill isn't one big block of text — it has three layers. Understanding this is what separates a Skill that works from one that confuses Claude or never triggers.
The first thing Claude checks in every conversation. It reads this tiny header to decide: is this Skill relevant right now? A good trigger = Skill fires automatically. A vague trigger = Skill never fires.
Name: Email Rewriter
Description: Rewrites emails to sound professional and warm. Use when someone asks to improve, fix, rewrite, or clean up an email.
Once the trigger fires, Claude reads your full instructions. This is where you write exactly how you want Claude to work — your steps, your rules, your output format. Keep it focused. This is your process, not a catch-all.
Your numbered steps → Your specific rules → What the output should look like. Not long reference docs or brand guides — those go in Layer 3.
Separate files Claude grabs only when the task calls for them — your brand voice doc, example outputs, tone references. Not loaded every time. This keeps Claude's responses fast and focused instead of bloated.
A brand voice document · Sample emails in your tone · A word list you never use · A template you want Claude to follow
Skills require one setting to be on first. Go to Settings → Capabilities and make sure "Code execution and file creation" is enabled. Without this, Skills won't work.
Available on free, Pro, Max, Team, and Enterprise plans. All plans can use Anthropic's built-in Skills. Pro, Max, Team, and Enterprise can also upload custom Skills.
The best Skills solve something you do over and over. Ask yourself: Have I explained this to Claude at least 5 times? That's your Skill. Good candidates: writing emails in your voice, formatting reports, creating captions in your tone.
Make a new folder on your computer. Inside it, create a plain text file called Skill.md. This is your Skill file — it has two parts: a metadata section at the top (name + description) and your instructions below it.
Top of file: name and description (what it does + when to use it)
Rest of file: your step-by-step instructions for Claude
That's it. Start simple. You can always add more files later.
Compress your folder into a .zip file. Then go to Customize → Skills, click the "+" button, select "Upload a Skill", and choose your zip. Done — it'll appear in your Skills list.
Zip the folder — not just the Skill.md file inside it. Claude needs to find the file inside a folder. If you zip the file directly, the upload works but the Skill never triggers.
Find your Skill in Customize → Skills and make sure it's toggled on. Then open a fresh chat and type something that should trigger it — without mentioning the Skill name. If Claude uses it automatically, it's working.
Don't say "use my email Skill." Just say "can you help me rewrite this email?" If Claude applies your Skill on its own — your trigger description is working perfectly.
Claude uses your description to decide when to activate your Skill. It needs to say what the Skill does and when to use it. Include the exact phrases someone would actually say. Too vague and it never fires.
"Helps with writing and content tasks."
"Rewrites emails to sound professional. Use when someone asks to improve, rewrite, fix, or clean up an email."
Write exactly how you want Claude to work, in numbered steps. Be specific. Don't explain why — just tell Claude what to do. Keep it focused on the workflow. Long reference material goes in a separate file.
1. Read the full email before doing anything.
2. Keep the original meaning — only change tone and clarity.
3. Use short sentences. Cut filler words.
4. End with a clear, polite call to action.
5. Never use exclamation marks.
Include a short example of what a perfect output looks like. Claude learns more from one real example than from five paragraphs of explanation. Show it what "done right" means. Put long reference docs in a separate file and mention them in your instructions.
For tone and voice examples, see the brand-voice.md file included in this Skill.
Don't try to make one Skill handle everything. Claude runs multiple Skills at once, so keep each one focused on a single workflow. Smaller and specific beats bigger and vague.
If Claude isn't triggering your Skill, make the description more specific with clearer trigger phrases. Re-upload and test again. The best Skills are tweaked over time, not written perfectly once.
Before building custom Skills, turn on the pre-built ones from Anthropic (Excel, PowerPoint, Word, PDF) in Customize → Skills. Get comfortable with how they feel before creating your own.
If your Skill file is getting really long, that's a sign to move the heavy stuff into a separate reference file. Your main instructions should be scannable in under a minute.