Setup Mod

Install the MCP mod + Fabric API (Step 2 of 4)

This is Phase 2 of the four-phase Minecraft Java MCP setup. It assumes Phase 1 (setup-fabric) is done: Fabric is installed and the mods/ folder exists. You should have, written down:

• the chosen Minecraft version (e.g. 26.1.2);
• the mods-folder path (single-player) or the `` root with its

mods/ folder (dedicated server).

If either is missing, get it before continuing. Work interactively — confirm each download before moving on.

What you're installing

The MCP server is delivered as a Fabric mod. It needs exactly two jars in mods/, both matching the same Minecraft version:

1. The MCP mod — minecraft-fabric-mcp-+.jar.
2. Fabric API — the mod's only dependency.

> Match the Minecraft version on both jars. A jar built for 26.1.2 will > not load on 1.21.11, and vice versa. The version suffix after the + must > equal the version chosen in Phase 1.

Step 1 — Download the MCP mod jar

From the mod's releases:

Pick the asset whose filename ends in +.jar — e.g. minecraft-fabric-mcp-0.1.0+26.1.2.jar for Minecraft 26.1.2. Pin to a specific release tag rather than tracking latest, so the version stays in lockstep with Minecraft and Fabric API.

Step 2 — Download the matching Fabric API jar

From Modrinth:

Filter by your Minecraft version and download the Fabric API jar for it — e.g. fabric-api-0.149.1+26.1.2.jar. The exact Fabric API build doesn't have to be the newest, but its Minecraft version must match.

Step 3 — Put both jars in mods/

Copy both jars into the mods/ folder from Phase 1.

Single-player — the platform path:

| OS | Path | | -- | ---- | | Windows | %appdata%\.minecraft\mods\ | | macOS | ~/Library/Application Support/minecraft/mods/ | | Linux | ~/.minecraft/mods/ |

Dedicated server — /mods/:

mkdir -p /opt/fabric-mcp/mods
# copy both jars into it

The folder should now contain exactly these two jars (plus any other mods the user already runs):

mods/
├── fabric-api-0.149.1+26.1.2.jar
└── minecraft-fabric-mcp-0.1.0+26.1.2.jar

Confirm with the user that both files are present and that the version suffixes match each other and the Minecraft version.

Step 4 — Quick load check (optional but recommended)

If the user wants to confirm the mod loads before configuring it:

• Single-player: launch the Fabric profile and load any world.
• Dedicated server: java -Xmx2G -jar fabric-server-launch.jar nogui.

In the log, look for the mod's startup lines:

[minecraft_fabric_mcp] MCP server config loaded from .../config/minecraft_fabric_mcp/config.json
[minecraft_fabric_mcp] Registered N MCP tools (M skipped due to version/module constraints)
[minecraft_fabric_mcp] MCP server listening at http://127.0.0.1:8765 (...)

Seeing the listening line means the mod loaded and the embedded MCP server started. (Phase 3 covers configuring it and verifying /healthz.) If the game crashes on load, the usual cause is a version mismatch between the mod jar, the Fabric API jar, and Minecraft — re-check the + suffixes.

Wrap up

Confirm with the user:

• [ ] MCP mod jar for the chosen Minecraft version is in mods/.
• [ ] Matching Fabric API jar is in mods/.
• [ ] Both version suffixes match each other and the Minecraft version.
• [ ] (Optional) The mod loaded and logged the MCP listening line.

Hand off: Phase 2 is done — the mod is installed. The next step configures the MCP server (config.json), launches it, and verifies it's reachable. Offer to continue with the setup-server skill now.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: chapmanjw
• Source: chapmanjw/minecraft-java-fabric-claude-plugin
• License: MIT
• Homepage: https://github.com/chapmanjw/minecraft-java-fabric-mcp-server

Install and usage instructions live in the source repository linked above.