Minecraft wiki entry for Creating_a_data_pack, associated text: This file is written in JSON! This tutorial does not go into specifics about the format now, but be aware about how things are laid out. Be very careful not to forget quotation marks, colons, and curly or square brackets. Make sure to not write trailing commas. Missing one of these can lead to your data pack not working correctly! To check your files you can use a JSON validator, such as the one found on JSONLint.