The assets/minecraft/font/include/unifont.json
file obtained from resources.download.minecraft.net
contains a trailing comma, which is invalid JSON. The game reads this file in lenient mode, but this is not guaranteed for external tools.
How to reproduce
Download https://resources.download.minecraft.net/f4/f40266672fa6cd5c678cbfd5a7fdcfe06e30c629
Open the file in a text editor
Notice on line 101 that there is a trailing comma
Expected behavior
I expected that all JSON files in assets would be valid
Can confirm:
[media]