Skills: the same job, your way
A brief describes one job. A skill describes how a job is always done here, and Claude picks it up when the job comes round again.
You have been writing the same instructions into every brief: which columns, what clean means, how the regions are spelled. That is not a brief any more, it is a procedure, and a procedure belongs in a file.
What a skill is
A folder with a markdown file in it. The file has a short header saying what the skill is called and when to use it, then the steps. Nothing else is required, and there is no code involved unless you want some.
---
name: Monthly sales clean-up
description: Combine monthly sales CSV exports into one spreadsheet with consistent columns and regions. Use when asked to prepare, clean or combine the monthly sales data.
---
# Monthly sales clean-up
1. Read every CSV in the folder you were given.
2. Keep these columns: date, region, product, units, revenue.
3. Dates become YYYY-MM-DD.
4. Treat "APAC", "Asia Pacific" and "asia-pac" as one region, APAC.
5. Drop rows with no revenue figure, and count them.
6. Write one spreadsheet, then state the row count before and after
and the number of rows dropped.
Stop and ask if a file has columns that do not match this shape.Read the steps and notice how ordinary they are. This is not prompt engineering, it is the note you would leave for somebody covering your job, written in the order the work actually happens.
Where it lives, and who gets it
For the Claude apps, a skill is a folder packaged as a zip with the markdown file inside it, and you enable it under Customize, then Skills. It needs code execution turned on. Once enabled it is available to your sessions without being mentioned.
The same shape works elsewhere. The format is an open standard, so a procedure written here is not stranded in one product.
Skill or project instruction
| Put it in | When |
|---|---|
| Project instructions | It is true for this job and only this job |
| A skill | It is a procedure with steps, used whenever this kind of work appears |
| Global instructions | It is true for everything you ever ask |
The sales clean-up is a skill because it is a sequence with rules. Who reads the summary is a project instruction because it is a fact, not a procedure.
- Take the repeated half of your brief and rewrite it as numbered steps.
- Count how much shorter the brief becomes once those steps live somewhere else.
Little by little, you're building something great.