If you’re building AI workflows — prompt sequences, story bibles, MCP configs, Obsidian templates — you’re going to run into YAML. It’s the configuration language behind most of the tools in the indie author stack, and it trips people up because it looks simple but punishes you for invisible mistakes (a wrong indent, a missing space after a colon).

This post is a two-part resource: a reference guide and an interactive quiz.

Quick Reference

The Notion embed below is a living cheat sheet — key-value pairs, lists, nested objects, multi-line strings, and the gotchas that catch people most often.

Interactive Quiz: Syntax Master

Reading syntax rules is one thing. Writing them from memory is another. The quiz below walks you through three core YAML patterns — key-value pairs, lists, and nested data — framed as building a story bible for a fantasy world.

Each lesson shows you the pattern, then the challenge asks you to write it yourself in a live code editor with syntax highlighting. You’ll build a character, update an inventory, and modify nested world-building data.

Or open it directly at carlo-v-santiago.com/widgets/quiz-yaml-syntax/.