See a Horse's Stats when right-clicking them.
Note that on tamed horses, right-clicking will mount them, which overrides this display.
This can be circumvented by feeding the horse, using a lead, or shift-right-clicking (and closing the inventory after it opens)
This is a limitation of the datapack and circumventing it would either require spamming the client's chat (which I did not want to do), or using gaudy workarounds with something like a fishing pole.
Health is displayed in Max Half-Hearts. Note that Minecraft's display of Horse Health rounds down to full hearts. A horse's Health can range from 15 to 30
Jump is displayed as the internal value, which ranges from 4.0 to 10.0. There is no easy conversion factor. To quote the wiki: "A jump strength of 5.0 is enough to clear 1 9⁄16 blocks, while 10.0 is enough to clear 5 1⁄4 blocks."
Movement Speed is displayed in Blocks/Second, and can range from 4.85 to 14.60. This does not take into account Potions of Swiftness, Ice, or modded enchantments.
The minimum and maximum ranges here are Vanilla. Mods that change horse's min/max stats will be shown properly, unless they alter them outside of directly changing the horse's attributes.
Run "/function horsestats:start" in a world with the datapack in it to enable the datapack. This only has to be done once.
