rpg.pizza

Make your own rulebook

rpg.pizza builds the sheet of any system from a rules file: a JSON with the book's data (ancestries, classes, spells, items…) and scripts that do the math. You don't need to code: an AI agent such as Claude Code writes the file from your book.

Before you start: copyright

  • Only use books you bought or that have an open license. Don't use pirated PDFs or copies distributed without permission.
  • A file made from a copyrighted book is for personal use, at your own table. Don't publish it, share it online or sell it. To share, prefer openly licensed systems (SRDs, Creative Commons) and follow each license's terms.
  • Only ask the AI to translate when there is no official edition in your language. If there is one, buy and use the official edition.
  • rpg.pizza doesn't host, distribute or review rules files, and isn't affiliated with any publisher. Each game master is responsible for the file they upload. This guide is not legal advice.

What you need

  1. An AI agent that reads files and runs commands (Claude Code or another).
  2. The book (typically a PDF) in the main edition, the source of every rule and number (usually the original, often in English).
  3. If you want the sheet in other languages: the official editions in those languages, only for names and texts.

The agent downloads what it needs from rpg.pizza on its own: the schema, which explains the format and the API, and the example file it follows. Both links are already in the prompt.

Step by step

  1. Create a folder with the books.
  2. Open the agent in that folder and send the prompt below, replacing what's in brackets.
  3. Test the file in the sheet editor: create characters, level up, check the numbers against the book.
  4. Ask for fixes with concrete examples ("at 3rd level, the fighter should have 24 HP").
  5. Done: create a table with the file.

Big systems work better in parts: character creation first, then levels, gear and spells.

The prompt

Create an rpg.pizza rules file for the [NAME] system from the books in this folder.

1. Read the schema at https://rpg.pizza/ruleset-v1 (format, Lua API and conventions) and the example file at https://rpg.pizza/rulesets/example.ruleset.json. Follow the same style: book data in catalogs, rules in Lua scripts, stable English ids. The sheet is for building and playing a character: rules text goes where the player uses it (descriptions, hints), not in sections that restate the book.
2. The main book is [book-en.pdf]. It is the only source of rules and numbers. Convert it to text once, keep that file and search it as you go instead of rereading the book. Text extraction can drop or garble characters: check the numbers against the book's own examples.
3. The other books ([book-es.pdf]) are official editions, only for translating names and texts. Never use them as a source of rules.
4. File languages: [en, es] (the first one is the main language).
5. Start with character creation; then the rest of the book (for example levels, gear and spells). Check every number against the book.
6. Don't invent rules. Leave out what can't be modeled and tell me what was left out.
7. Validate the file against the schema (JSON Schema 2020-12) and run the scripts with an empty sheet and a few characters, in the simplest way that works: the goal is to catch mistakes in the file, not to rebuild the site. Fix it until it passes with no errors.

Deliver a single [system].ruleset.json file.