# Setup Mod

> >-

- **Type:** Skill
- **Install:** `agentstack add skill-chapmanjw-minecraft-java-fabric-claude-plugin-setup-mod`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [chapmanjw](https://agentstack.voostack.com/s/chapmanjw)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [chapmanjw](https://github.com/chapmanjw)
- **Source:** https://github.com/chapmanjw/minecraft-java-fabric-claude-plugin/tree/main/skills/setup-mod
- **Website:** https://github.com/chapmanjw/minecraft-java-fabric-mcp-server

## Install

```sh
agentstack add skill-chapmanjw-minecraft-java-fabric-claude-plugin-setup-mod
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# 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/`:

```sh
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](https://github.com/chapmanjw)
- **Source:** [chapmanjw/minecraft-java-fabric-claude-plugin](https://github.com/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.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-chapmanjw-minecraft-java-fabric-claude-plugin-setup-mod
- Seller: https://agentstack.voostack.com/s/chapmanjw
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.