From Datapack to Katton

If you already know vanilla datapacks, Katton should feel familiar: you still reload quickly, you can still call command-like helpers, and you can keep existing .mcfunction files while moving the parts that need real code into Kotlin.

The big difference is that Katton lets you stop encoding all logic as command strings. You can write functions, store values in variables, react to events, work with real entity objects, and use hot-reloadable APIs that reach far beyond vanilla datapacks.

NOTE

Paper supports server-side datapack-style APIs and events, but it cannot register custom items, blocks, entities, or client features because a vanilla client cannot receive those registry entries.

Migration Map

Datapack habit	Katton replacement	Start here
data/<namespace>/function/*.mcfunction	.kt files with @ServerScriptEntrypoint functions	Project Structure
Long command chains	Kotlin functions, loops, and command helpers	Translating mcfunction to Kotlin
Vanilla commands	top.katton.api.dpcaller helpers	Calling Vanilla Commands
@e[...], @a[...]	EntitySelectorBuilder and real entity objects	Selectors and Entity Access
Scoreboards, tags, NBT, storage	Scoreboards when useful, Kotlin values for logic, NBT APIs for data access	Scoreboards, Tags, NBT, and Storage
#load, #tick, schedule function	Server lifecycle and tick events	Replacing Load, Tick, and Schedule
Recipe and loot JSON edits	modifyRecipe, modifyLootTable, and related APIs	Recipes, Loot Tables, and Datapack Mutations
Existing datapack libraries	Keep them and call runFunction while migrating gradually	Keeping Existing Datapacks
Datapack limitations	Events, registries, client rendering, injection, pack UI	Going Beyond Datapacks

A Good First Migration

Start with a small utility function, not your entire datapack. Pick something that is annoying in .mcfunction, such as a selector-heavy loop, a scoreboard calculation, or a command chain that needs branching.

1. Create a script pack.
2. Add one @ServerScriptEntrypoint function.
3. Recreate the behavior in Kotlin.
4. Reload with /katton reload.
5. Keep the rest of the datapack unchanged until the new script feels solid.

Set Up a Script PackMap datapack folders to Katton filesTranslate Your First FunctionTurn command chains into Kotlin logic