Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add chapmanjw/minecraft-java-fabric-claude-plugin --skill setup-fabricgit clone --depth 1 https://github.com/chapmanjw/minecraft-java-fabric-claude-pluginWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/chapmanjw/minecraft-java-fabric-claude-plugin/setup-fabric)<a href="https://agentmods.dev/skills/chapmanjw/minecraft-java-fabric-claude-plugin/setup-fabric"><img src="https://agentmods.dev/badge/skills/chapmanjw/minecraft-java-fabric-claude-plugin/setup-fabric/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/chapmanjw/minecraft-java-fabric-claude-plugin/setup-fabric"><img src="https://agentmods.dev/badge/skills/chapmanjw/minecraft-java-fabric-claude-plugin/setup-fabric.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00080 | $0.01507 |
| Opus 5.5 | $0.00032 | $0.00603 |
| Sonnet 5.5 | $0.00016 | $0.00301 |
| Haiku 4.5 | $0.00008 | $0.00151 |
Grade A, and why
setup-fabric scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 147 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Install Minecraft Java + Fabric (Step 1 of 4)
You are guiding the user through the first of four setup phases. Work interactively: do one thing, confirm it worked, then move on. Do not dump the whole procedure at once.
The big picture — explain this first
The user is building a stack that lets Claude read and change a live Minecraft Java Edition world. Unlike a separate server process, the MCP server is a Fabric mod that runs inside Minecraft itself. There are four setup phases, one per skill, run in order:
| Phase | Skill | What it does |
|---|---|---|
| 1 | setup-fabric (this one) |
Minecraft Java Edition with the Fabric loader. |
| 2 | setup-mod |
The MCP mod jar + its matching Fabric API jar in mods/. |
| 3 | setup-server |
The mod's config.json, launched and verified on /healthz. |
| 4 | setup-connect |
Register the MCP server with Claude so the Java tools appear. |
Tell the user this is Phase 1, and that each phase ends by handing off to the next. Budget ~10 minutes for a single-player setup, ~20–30 for a dedicated server.
Pin your versions — say this out loud. The mod ships a separate jar per Minecraft version, built against that version's Fabric API. A Minecraft or Fabric update can break the modding surface the mod depends on. Pick a supported Minecraft version, pin it, disable auto-update for that profile, and upgrade Minecraft, the Fabric API jar, and the mod jar together.
Gather context
Ask the user, before downloading anything:
- Single-player or dedicated server?
- Single-player (recommended default): Claude edits the world you play in, on your own machine. Loopback only, no token, no firewall changes. ~10 minutes.
- Dedicated server: a headless Minecraft server (for friends, or to keep the MCP endpoint up 24/7). LAN/remote access with a bearer token. Branch the rest of this skill on their answer.
- Which Minecraft version? The mod supports 1.21.11, 26.1.1, 26.1.2, and 26.2. Default to the newest the user is comfortable with (26.2). Record the exact version — it must match the mod jar and Fabric API jar in Phase 2. The mod jar declares an EXACT Minecraft dependency, so a mismatch is refused at load with a clear message rather than failing later.
- (Dedicated server only) What OS and where? Linux or Windows; same machine as Claude, LAN box, or cloud VM. The host needs a JDK: Java 21 for 1.21.11, Java 25 for 26.1.x. (Single-player uses the launcher's bundled runtime — no separate JDK needed.) The connect step (Phase 4) cares where it runs, so note their answer.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 147 lines · 80 tokens per session scan A 90c334557e62
setup-fabric is a skill published in the GitHub repository chapmanjw/minecraft-java-fabric-claude-plugin (8 stars, last pushed 1mo ago), licensed MIT. It adds 80 tokens to every session and 1,507 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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