weaponlab-mcp

Weapon Lab

An MCP server that finds and fixes first-person weapon bugs behind a gate: hands off the gun, a magazine crooked in its well, a blade held wrong, arms covering the screen.

Each bug becomes a case: a metric, a weapon, an action and a pass rule. Your game's own probe measures the weapons. The Gate passes a change only when its target cases pass and nothing else got worse. Fix each kind of bug once, then check every weapon with it.

Weapon Lab never runs your game itself. You write a small probe for your engine that follows the probe contract: a job file in, a rows file out. Everything else works on what the probe writes back.

What it does

Group	Tools	What for
Gate	gate_run, gate_verdict, gate_propose, gate_approve, gate_set_baseline, gate_cases, ...	Keeps the bugs as cases, measures, compares against a baseline, judges a change, records a person's approval.
Probe	probe_run, probe_plan, probe_status	Starts your game's probe. Tries a fix before it is written: tuned fields, staged assets, screenshots, parts dumps.
Rig Lab	rig_pieces, rig_facts, rig_align, rig_part_line, rig_fist	Reads the posed weapon from a parts dump: its pieces, real-world facts (the magazine behind the barrel), a magazine's line into its well, a hilt in the fist.
Motion Lab	motion_roll, motion_roll_profile, motion_roll_set, motion_track, motion_render	Rebuilds clips in Blender: turns a hand about its forearm inside the forearm's range, puts a sliding part back on its axis.
Specs	spec_list, spec_read, spec_validate, spec_write	One file a weapon: marks (grip, support), anchors (pieces to find), facts, limits.
Contract	contract_check	Checks a probe's job, rows or parts dump.

Try it on the demo

The demo is a toy game with two planted bugs and a probe in about 150 lines. It needs no engine.

pip install -e .
cd examples/demo
weaponlab gate run probe,rig

(python -m weaponlab works the same when pip's scripts folder is not on your PATH.)

The rifle's left hand misses its handguard by 3.75 cm. The knife's hilt lies 90 degrees across the fist. tests/test_demo.py walks the whole loop: measure, find the fix, try it by tune, judge it.

Use it in your game

• weaponlab init in your project. It writes weaponlab.json and empty data files.
• Write your probe from the contract, starting from examples/demo/probe/demo_probe.py. Set its command in weaponlab.json.
• List your weapons in weaponlab/data/weapons.json and their actions in actions.json.
• Add a case for each bug you know. Measure everything once and set the baseline.
• Fix through the loop: try by tune or staging, look at the screenshots, propose, approve, import.

Check your probe on its own with weaponlab contract job|rows|parts <file>.

Add it to an MCP client

{"mcpServers": {"weaponlab": {"command": "weaponlab-mcp", "env": {"WEAPONLAB_PROJECT": "C:/path/to/your/game"}}}}

Setting	Meaning
WEAPONLAB_PROJECT	The project folder with weaponlab.json. The current folder by default.
WEAPONLAB_BLENDER	Blender, for Motion Lab. Found on the PATH or in the usual install folders otherwise.

Requirements

• Python 3.10 or later.
• Blender 4.4 or later for Motion Lab and renders. Nothing else needs it.
• Hand bones named as Unreal's mannequin names them (hand_r, index_01_r, lowerarm_r) for the fist measure and the forearm roll.

Where it came from

Weapon Lab is the general part of the tools built for ToangTown, an Unreal 5.8 game with 46 weapons. Its first probe is ToangTown's. The contract's lessons come from that probe. Pose Lab (poselab-mcp) answers the body's side: clipping, the view, a grip solver. The Gate can use it as a provider.

License

MIT