Raw protocol

The MCP server is a thin layer over a WebSocket JSON-RPC API, so you can also drive the game from your own scripts or CI without an agent.

• Client: ws://127.0.0.1:25599/. Dedicated server: ws://127.0.0.1:25598/.
• Send {id, method, params}. Receive {id, result} or {id, error: {message, type, stack}}.
• Requests run concurrently and responses are matched by id.
• Method names and params are the Method column of the client and server tool tables.

const ws = new WebSocket('ws://127.0.0.1:25599/');
ws.onopen = () => ws.send(JSON.stringify({ id: 1, method: 'status', params: {} }));
ws.onmessage = (e) => console.log(JSON.parse(e.data));

scripts/lib.mjs is a tiny promise client for Node 22+ with no dependencies:

import { connect } from './lib.mjs';

const mc = await connect();
await mc.call('world.create', { name: 'ci-test', flat: true });
const r = await mc.call('command', { command: 'give @s minecraft:diamond' });
console.log(r.output);
mc.close();

Every game-state access hops to the render thread with Minecraft.execute(); nothing blocks the render thread, and waits are checked once per client tick.