Creating Practical Skills
Introduction
In the previous unit, we explored the fundamentals of the Skills system: how Skills differ from custom commands, their file structure, and when to create them versus using CLAUDE.md. Now it is time to build something real.
In this lesson, we will move from theory to practice by creating two actual, functional Skills: a CSV analysis Skill and a visualization standards Skill. Along the way, we will learn how to write descriptions that help Claude select Skills automatically, how to define tool permissions properly, and how to verify that our Skills work as intended.
Practical vs. Artificial Skills
The best Skills solve real problems that occur regularly in actual projects. For this lesson, we focus on two such Skills:
- CSV Analyzer: Analyzes CSV data with summary statistics and insights — a common data analysis task
- Sci-Viz: Creates publication-ready scientific visualizations — essential for research papers
These differ from educational exercises like "convert strings to uppercase" or "add a fixed header to a file." Practical Skills embed domain knowledge and address recurring needs, which is exactly what makes them worth creating.
Creating Your First Skill: CSV Analyzer
Let's create a Skill that analyzes and summarizes CSV data with statistical insights. We will place this Skill in the project-specific directory so it is available for all team members working on this project.
The Skill resides in a dedicated folder with a clear, descriptive name:
Every Skill starts with YAML frontmatter that provides metadata for Claude's selection system. Here is how we begin our CSV analysis Skill:
This frontmatter establishes three critical pieces of information. The name uniquely identifies this Skill, the description tells Claude when to use it, and allowed-tools specifies which capabilities this Skill can access. We will explore each of these fields in detail next.
Writing Clear Descriptions for Automatic Selection
