MCP Fabric (Minecraft)

mcpfabric MCP server

Bridges an MCP client (Claude Desktop / Claude Code / any MCP host) to the in-game HTTP bridge exposed by the mcpfabric mod (Fabric / NeoForge), publishing ~50 tools to observe and control Minecraft, plus an agent runtime with persistent memory, goals, a world map and background jobs (see docs/AGENT.md). Requires Node.js ≥ 22.16.

Install from npm

npx -y mcpfabric-mcp-server          # or: npm install -g mcpfabric-mcp-server && mcpfabric

In an MCP client config:

{  "mcpServers": {    "mcpfabric": {      "command": "npx",      "args": ["-y", "mcpfabric-mcp-server"],      "env": { "MCPFABRIC_TOKEN": "paste-the-token-from-the-mod-config" }    }  }}

Build from source

npm installnpm run build       # -> dist/index.jsnpm run typecheck   # tsc --noEmit (sources and tests)npm test            # unit tests + agent jobs against a simulated world

Run

The MCP client normally launches this process. Manually:

MCPFABRIC_URL=http://127.0.0.1:25599 MCPFABRIC_TOKEN=<token> node dist/index.js

Environment

Architecture

src/tools.ts is the single source of truth for the tool catalogue: each entry maps an MCP tool to a bridge RPC method plus a zod input schema. src/index.ts registers every entry generically (forwarding args to POST /rpc) and renders results as JSON, except screenshot which returns an image content block. src/bridge.ts is the HTTP client; src/config.ts reads env config.

src/agent/ is the agent runtime: its tools (agent/tools.ts) run in this process, store state in SQLite (node:sqlite) and drive the game through the same bridge. test/fake-world.ts simulates the bridge contract so jobs are tested without a game.

src/script/ is code mode: run_script runs a model-written JavaScript program in QuickJS (WebAssembly, quickjs-emscripten), which reaches the game only through the catalogue methods of src/tools.ts; save_skill / run_skill keep programs per world in the agent database.

Keep tool names/methods in sync with the Java handler registry in the mod (dev.mcpfabric.handlers.* and dev.mcpfabric.client.handlers.*).