Requirement

Details

Node.js 18+

nodejs.org

Java 17+

Required for decompilation and remapping • Verify with java -version • Adoptium or Oracle JDK

Method

Command

NPM (Recommended)

npm install -g @mcdxai/minecraft-dev-mcp

NPX (No Install)

Use npx -y @mcdxai/minecraft-dev-mcp directly in config

From Source

See the Development section

Platform

Config Path

Windows

%APPDATA%\Claude\claude_desktop_config.json

macOS

~/Library/Application Support/Claude/claude_desktop_config.json

Linux

~/.config/Claude/claude_desktop_config.json

Feature

Description

On-demand decompilation

Download, remap, and decompile any Minecraft version (1.14+) on first use — cached for instant access afterward

Multiple mapping namespaces

Yarn, Mojmap (official), Intermediary, and obfuscated — translate any symbol between them with find_mapping

Decompiled source access

Retrieve Java source for any Minecraft class with optional line-range filtering

Mod JAR analysis

Analyze Fabric, Quilt, Forge, and NeoForge mods — metadata, mixins, dependencies, entry points — and decompile them

Mixin & Access Widener validation

Validate Mixin annotations and .accesswidener files against decompiled source with error reporting and fix suggestions

Version diff

Class-level and AST-level diff between any two Minecraft versions — method signatures, field changes, breaking changes

Full-text search

SQLite FTS5 indexes for fast BM25-ranked search across Minecraft and mod source

Workflow

Steps

First-time source access

Call get_minecraft_source — server downloads, remaps, and decompiles (~5 min first run). Subsequent requests for the same version return in ~50 ms from cache.

Analyze a third-party mod

analyze_mod_jar → remap_mod_jar → decompile_mod_jar → search_mod_code or index_mod + search_mod_indexed

Validate a Fabric mixin

analyze_mixin with your Java source or file path — validates targets, injection points, and method selectors against the decompiled MC version.

Find breaking changes between versions

compare_versions for a high-level overview, then compare_versions_detailed scoped to specific packages for full AST-level diffs.

Fast broad search

index_minecraft_version once, then search_indexed with FTS5 queries: entity AND damage, "onBlockBreak", tick*, BlockEntity NOT render.

Translate obfuscated names

find_mapping with sourceMapping: "official" to look up the Yarn or Mojmap equivalent for any class, method, or field.

Version Range

Yarn

Mojmap

Notes

1.14 – 1.21.11

Full support

Full support

Obfuscated — two-step remapping required (official → intermediary → named)

26.1+

Not available

Full support

Deobfuscated by Mojang — no remapping needed, classes already human-readable

Environment Variable

Description

CACHE_DIR

Override the default cache directory location

LOG_LEVEL

Logging verbosity: DEBUG, INFO, WARN, ERROR

Task

Command

Install dependencies

npm install

Build

npm run build

Dev mode (hot reload)

npm run dev

Tests

npm test

Issue

Solution

Java not found — Java 17+ is required but not found

Install Java 17+ from Adoptium • Verify with java -version • Ensure java is on your PATH

Decompilation fails

Check available disk space (~500 MB per version) • Review %APPDATA%\minecraft-dev-mcp\minecraft-dev-mcp.log • Force re-decompile by passing "force": true

Yarn not available — Yarn mappings not available for version X

Yarn is only supported for 1.14–1.21.11 • Use mojmap for 26.1+ versions

Class not found

Use the fully qualified class name (e.g., net.minecraft.world.entity.Entity) • Verify the version is decompiled

Registry returns no data

Registry names use singular form: block, item, entity — not blocks, items, entities

WSL path error

Both /mnt/c/path/to/file and C:\path\to\file are accepted for all JAR path parameters

Project

Details

VineFlower

Modern Java decompiler by the Vineflower Team

tiny-remapper

JAR remapping tool by FabricMC

Yarn Mappings

Community-maintained mappings by FabricMC

MCP SDK

Protocol implementation by Anthropic