2026-03-29 21:49 Tags:Technical Literacy

What is YAML?

YAML (short for “YAML Ain’t Markup Language”) is a simple, human-readable format for writing structured data. It uses indentation and key-value pairs instead of complex syntax like HTML or JSON.

A basic example:

name: John
age: 30
job: Designer

That’s it — key: value pairs, plain and simple.

---

What is “Frontmatter”?

Frontmatter is a block of YAML placed at the very top of a file, sandwiched between two sets of triple dashes (---). It’s essentially metadata about the file — information that describes the file itself rather than being the main content.

---
name: my-skill
description: This skill helps write emails
author: Jane
---

# The actual content of the file starts here...

Everything between the --- lines is the frontmatter. Everything after is the real content.

---

In the context of Claude Skills

When you create a SKILL.md file, the YAML frontmatter tells Claude the who/what of the skill at a glance — without reading the whole file:

---
name: email-writer
description: Helps draft professional emails in a concise tone
---

This matters because of how Claude loads Skills efficiently — it only scans the frontmatter first (name + description) to decide if a skill is relevant to your current task, then loads the full instructions only if needed. It’s like a book cover before reading the whole chapter.

---

Why triple dashes?

The --- is just a widely adopted convention (originated from Markdown and static site generators like Jekyll) to signal “this section is metadata, not content.” It’s a separator that tools and AI can reliably detect.

---

In short: YAML frontmatter = a small labeled header at the top of a file that describes what the file is, written in a clean key: value format. Nothing more complicated than that!