Content kinds (registries)

A content kind is a typed builder that clones a vanilla base and emits a new definition. This is RSMM’s analog of a Minecraft registry: you don’t hand-author engine bytes, you declare “a new item like Knife” and the SDK materializes it.

import rsmm.sdk as sdk
m = sdk.Mod(id="RubyMod", name="Ruby Mod")
m.item("RubyDagger", base="Knife", name="Ruby Dagger")
m.enemy("FastRat", base="Rat", name="Fast Rat")
m.commit()

Available kinds include item, enemy, boss, hero, map, plus the asset kinds texture and model, and the grouping kind tag. The full, current list and signatures are in the generated SDK reference.

Confidence — the RSMM twist

Minecraft registries always work; RSMM kinds describe a reverse-engineered byte format, so each kind carries a confidence:

Confidence	Meaning	Requirement
confirmed	Emitted bytes verified in-game	usable directly
experimental	Plausible, not fully verified	needs Mod(..., experimental=True)
guess	Schema partially understood	needs experimental=True; may crash

rsmm lint enforces the opt-in gate, so you can’t accidentally ship a guess kind without acknowledging the risk.

Minecraft analogy

m.item(base="Knife") ≈ DeferredRegister registering an item that copies an existing one’s properties. The base is the vanilla prototype; **fields override specific values. See Coming from Minecraft.

Common problems

Caution

• kind 'x' is 'experimental' error. Add experimental=True to your Mod(...) — and expect to test in-game.
• New content doesn’t appear in-game. Most kinds also need engine-side registration (e.g. a versiondef / UsedRscList entry). The applier handles the confirmed pipelines; experimental kinds may not be wired end-to-end.
• Unknown base. The base must name a real vanilla definition. Browse candidates with the relevant rsmm listing command.

Related

• Tags — group content across mods.
• Mods ship data, not code — why this is declarative.
• Authoring mods — the full how-to.