setup-mod

name	setup-mod
description	Step 2 of 4 of the Minecraft Java MCP setup. Download the minecraft-java MCP mod jar and its matching Fabric API jar and install both into the Minecraft mods folder. Use when the user has Minecraft Java with the Fabric loader ready and needs the MCP mod and Fabric API installed.

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 <server> 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-<modver>+<mc-version>.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: https://github.com/chapmanjw/minecraft-java-fabric-mcp-server/releases

Pick the asset whose filename ends in +<your-mc-version>.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: https://modrinth.com/mod/fabric-api/versions

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 — <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 +<version> 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.