It would be nice to be able to blacklist some entities or items, like the "MmmMmmMmmMmm" mod's target dummy, from giving experience.
In our modpack, we could just keep shooting the target dummy with arrows until we maxed out a crystal bow. Would be nice to prevent something like that, if possible?

If you don't use CraftTweaker, you can also add to the tag via datapacks.

Add a file entity_blacklist.json in the datapack in the location crystal_tools/tags/entity_types that looks like

{
  "values": [
    "minecraft:armor_stand"
  ]
}

I will add this to the readme as well

Yeah that should be possible. I can add a blacklist tag that you should be able to add entities to.

Added in 1.20.1-1.6.1

For reference to anyone else who wants to use your change, I blacklisted the target dummy as follows:

1. Install CraftTweaker mod
2. Create a new .zs file in ./scripts/
3. add the following line in the .zs file:
   <tag:entity_types:crystal_tools:entity_blacklist>.add(<entitytype:dummmmmmy:target_dummy>);
   (Just replace "dummmmmmy:target_dummy" with whatever mob or entity you want to blacklist.)

The .zs file is executed/applied when your world loads