Full-stack Minecraft mod development skill for NeoForge (1.21+), Fabric (1.21+), and legacy Forge 1.20.1. Scaffolds new mods, adds custom blocks, items, entities, recipes, commands, GUIs, dimensions, and data generation. Knows NeoForge DeferredRegister + event-bus patterns, Forge 1.20.1 MDK/FMLJavaModLoadingContext patterns, and Fabric Registry + ModInitializer patterns. Use when the user asks to create a Minecraft mod, add a feature to an existing mod, fix a mod bug, generate JSON assets/data, support Forge 1.20.1, or migrate between modding platforms. Prefer NeoForge unless the user specifies Fabric, Forge 1.20.1, or Multiloader.
Write Minecraft vanilla commands, NBT scripts, scoreboards, and complex execute chains for use in command blocks, chat, or .mcfunction files. Covers full execute subcommand reference (as/at/in/positioned/rotated/facing/anchored/if/unless/store/run), selector arguments with all filter options, scoreboard objectives and operations, NBT path syntax for entities/blocks/storage, schedule and forceload commands, tellraw/title JSON text components, bossbar, team management, item modification commands, attribute commands, particle/playsound effects, and RCON scripting. Targets Minecraft 1.21.x Java Edition. Use for command-only work; for full function/advancement/recipe systems use the minecraft-datapack skill instead.
Create custom world generation content for Minecraft 1.21.x including custom biomes, dimensions, noise settings, surface rules, placed/configured features, carvers, structure sets, and biome modifiers. Covers both the datapack-only approach (JSON worldgen files) and the mod-code approach (NeoForge BiomeModifiers, Fabric BiomeModification API, code-driven worldgen registration with DeferredRegister). Includes compact JSON patterns and validator-backed reference checks for biome, dimension, placed_feature, configured_feature, structure, structure_set, and biome_modifier files. Targets Minecraft 1.21.x with official Mojang mappings, with explicit verification required before applying 1.21.10-and-earlier biome or dimension JSON shapes to 1.21.11+ packs. Use when the user asks about Minecraft worldgen, custom biomes, datapack JSON for dimensions or features, or mod-based biome modification with NeoForge or Fabric.
Create, edit, and debug Minecraft vanilla datapacks for 1.21.x. Covers the full datapack format: pack.mcmeta, function files (.mcfunction), advancements, predicates, loot tables, item modifiers, recipe overrides, tags, damage types, dimension types, worldgen overrides, and structure sets. Handles function syntax, execute command chains, macro functions (1.20.2+), storage NBT, scoreboard operations, advancement triggers, pack format numbers, and /reload workflow. No Java or mod loader required — pure vanilla JSON and .mcfunction files. Use when creating or editing Minecraft datapacks, writing .mcfunction files, configuring loot tables or advancements, or any vanilla datapack development that does not need mod loaders.
Operate EssentialsX on Minecraft 1.21.x servers with safe, practical admin workflows. Covers module scope, install and version-alignment checks, Vault economy integration, kits/warps/homes/spawn operations, permissions patterns, moderation workflows (mute, jail, tempban), and common config pitfalls. Use when the task involves EssentialsX commands, config, permissions, economy, or moderation operations — not plugin development or general server deployment.
Build Minecraft mods targeting both NeoForge and Fabric simultaneously using the Architectury framework for Minecraft 1.21.x. Covers Architectury project structure (common/neoforge/fabric subprojects), ExpectPlatform annotation for platform-specific implementations, shared registry via Architectury's registration API, platform-specific entrypoints, architectury-loom Gradle plugin configuration, gradle.properties for both loaders, multi-jar publishing to Modrinth and CurseForge, and avoiding common pitfalls when sharing code. Use this skill when building a mod that must run on both NeoForge and Fabric with a single shared codebase.
Develop Minecraft server plugins using the Paper/Bukkit/Spigot API for Minecraft 1.21.x. Handles creating Paper plugins with JavaPlugin, event listeners with @EventHandler, commands, schedulers (sync/async/Folia-safe), Persistent Data Container (PDC), Adventure text components, Vault economy integration, BungeeCord/Velocity messaging, plugin.yml and paper-plugin.yml configuration, YAML config management, and Paper-specific enhancement APIs. Always targets Paper API 1.21.x (Java 21) with Gradle (Kotlin DSL). Plugins run server-side only and do not require client installation. Use when creating or modifying Minecraft server plugins, working with Paper/Bukkit/Spigot APIs, or developing server-side features involving event handlers, commands, or plugin.yml configuration.
Create and edit Minecraft resource packs for 1.21.x including custom block models, item models, blockstate definitions, textures (PNG format requirements), sounds.json, custom fonts, MCMETA animation files, OptiFine CIT (Custom Item Textures), and pack.mcmeta format. Covers the full block/item model JSON schema (parent, textures, elements, display, overrides), multi-layer items, GUI textures, GUI sprites, language files, shader integration (core shaders, Iris), and the pack format numbers for each 1.21.x version. Use to customize how Minecraft looks and sounds without mods.