Godot MCP Loop

godot-mcp-loop

Let AI agents edit your Godot 4 game and check their own work. An MCP server + Godot editor addon focused on the verification loop: change → run → observe → judge.

日本語 README · Tools · Scenarios · Clients · Security · Protocol

There are many Godot MCP servers that let an agent edit scenes. Few let it find out whether the edit worked. godot-mcp-loop gives the agent a play-tester's toolkit — launch the game, send real input, wait for conditions, read live state, take screenshots, collect errors — plus declarative scenario tests that return a pass/fail report with the failing value. Editing is deliberately conservative: every change is undoable, previewable, validated before it is applied, and sandboxed to your project.

What an agent can do

godot_status                                    → editor connected, Godot 4.7.2, main.tscn open
script_write res://player.gd (dry_run)          → unified diff; compile errors with line numbers if any
script_write res://player.gd                    → written (undoable)
game_run                                        → game running, runtime connected
game_input [{action: move_right, hold_ms: 1000}]
game_wait_for Player position:x > 250           → met after 0.8 s
screenshot                                      → (image)
logs_read source=game min_level=error           → []
scenario_run res://tests/move_right.yaml        → PASSED (7/7 steps)

Highlights

• Closed loop: game_run, game_input (actions, keys, mouse, with real timing; can record values every frame), game_wait_for (checked every frame, reports the last value on timeout), game_query, screenshot, logs_read.
• Scenario tests: YAML/JSON play-tests → per-step pass/fail, failure screenshot, game errors. Details.
• Safe editing: every edit goes through Godot's undo history; edit_undo only ever reverts edits made via MCP; dry_run everywhere; GDScript is compiled before it is written; property values are validated before anything changes.
• Sandboxed: localhost-only bridge with a per-session token; res:// paths only; no writes to .godot/, .git/ or the addon; no arbitrary-code-execution tool. Security notes.
• Doesn't freeze on errors: Godot's debugger pauses games on script errors; the addon logs the error and continues, so the agent sees it instead of hanging.
• No extra ports in the game: the game talks to the editor over Godot's own debugger connection.
• 41 focused tools rather than hundreds — easier for models to use well.

Requirements

• Godot 4.7 (tested on 4.7.2). 4.5–4.6 should work — the addon needs the Logger API added in 4.5 — but are not tested yet.
• Node.js 20+
• An MCP client: Claude Code, Cursor, Claude Desktop, Codex, Hermes Agent, …

Install

As a Claude Code plugin (Claude Code 2.1.275+; asks for your Godot project path once):

/plugin install godot-mcp-loop --marketplace AI-osho/godot-mcp-loop

The plugin registers the godot-loop MCP server and the agent skill; it runs the npm package, so keep the addon it copies into your project in step (the addon and server must share a version).

With npm (Node.js 20+): With npm (Node.js 20+):

Listed in the official MCP Registry as io.github.AI-osho/godot-mcp-loop — clients that browse the registry can add it from there; the steps below are the same.

1. Addon — the addon must match the server's version, so let the server copy it into your project and enable it:

   npx -y godot-mcp-loop@latest install-addon /ABS/my-game --skill
   

   --skill also adds the agent skill (step 5 below). The command prints the version to use next.
2. Client — register the server with that version, e.g. Claude Code:

   claude mcp add godot-loop -- npx -y godot-mcp-loop@<version> --project /ABS/my-game
   

   Other clients: docs/clients.md.
3. Open your project in the Godot editor and ask the agent to call godot_status.

From source:

1. Addon — copy addons/mcp_loop into your project's addons/ folder, then enable Project › Project Settings › Plugins › MCP Loop. The plugin registers an autoload MCPLoopRuntime (inactive in exported games).
2. Server —

   git clone https://github.com/AI-osho/godot-mcp-loop.git
   cd godot-mcp-loop/server && npm ci && npm run build
   

3. Client — e.g. Claude Code:

   claude mcp add godot-loop -- node /ABS/godot-mcp-loop/server/dist/index.js --project /ABS/my-game
   

   Other clients: docs/clients.md.
4. Open your project in the Godot editor and ask the agent to call godot_status.
5. Agent skill (recommended) — copy .claude/skills/godot-mcp-loop into your project's .claude/skills/ (or ~/.claude/skills/ for every project). It teaches the agent the loop, deterministic checks with game_step, scenario patterns and pixel art. It follows the Agent Skills format, so other agents that read skills can use it too.

Start a new game project

scripts/new-game.sh ~/games/my-game --name "My Game" --register-claude

creates a Godot project with the addon enabled, the agent skill, short AGENTS.md / CLAUDE.md files, a scenarios/ folder and an initial git commit, and registers the MCP server with Claude Code for that folder (--claude-config DIR for a separate Claude Code configuration). Then open it with godot -e --path ~/games/my-game.

For long builds the project also gets PROGRESS.md (goal, status, done, next, decisions, known issues), which the agent keeps current, and Claude Code project settings (.claude/settings.json): a session-start hook prints PROGRESS.md, the last commits and uncommitted changes into the agent's context — at startup, on resume, after /clear and after context compaction — the godot-loop tools run without permission prompts, and destructive shell commands (rm -rf, force push, git reset --hard, git clean) are denied. Claude Code applies the allow rule once you accept its trust prompt for the folder.

Try the demo

This repository is itself a Godot project with a tiny platformer (examples/platformer, arrow keys + Space). Open it in Godot, point the server at the repository root, and ask your agent to "run scenario_run on res://examples/platformer/scenarios/move_right.yaml" — then try intentional_failure.yaml to see a failure report.

A five-minute tour

1. Install the addon in your project folder (it copies addons/mcp_loop, enables the plugin and drops the agent skill into .claude/skills/):

   cd my-game && npx -y godot-mcp-loop@latest install-addon . --skill
   

2. Open the project in Godot (4.5+): godot -e --path . — the bridge starts with the editor and listens on 127.0.0.1.
3. Connect your MCP client to npx -y godot-mcp-loop@latest --project /absolute/path/to/my-game, then ask for godot_status: it should report the Godot version, the project and the scene the editor has open.
4. Ask for one change and one check: "add a coin to the level, then run scenario_run {"path": "res://scenarios/coins.yaml"}". A failing step comes back with the observed value and a screenshot.
5. Record it: run the same scenario with "movie": {} and "save_to": "res://qa/evidence/tour", then open qa/evidence/tour/movie.gif — the whole run, plus a contact sheet of the key frames.

Advanced samples

Five complete games live in examples/. Each was generated end to end by an AI agent through godot-mcp-loop from a single prompt — code, NES-style pixel art (image_write), input actions, test hooks and regression scenarios — and then verified independently: every scenario passes and random-input runs log no errors.

The 3D sample ships with the package, so you can open it without cloning this repository:

npx -y godot-mcp-loop@latest sample marble-3d ./marble-3d
cd marble-3d && npx -y godot-mcp-loop@latest install-addon . --skill && godot -e --path .

It is the game the 3D tools were built against: seven scenarios (7_gap_needs_jump.yaml proves a gap cannot be rolled over), a chase camera, coins, checkpoints, lives and a timed clear. npx -y godot-mcp-loop@latest sample lists everything bundled.

Play one with game_run {"scene": "res://examples/shooter/shooter.tscn"} (or open the scene and press F6) and replay its checks with scenario_run {"path": "res://examples/shooter/scenarios/4_boss_clear.yaml"} — or all of them with {"path": "res://examples/shooter/scenarios"}. Controls and details: examples/README.md.

Tools

Full reference: docs/tools.md.

Headless / CI

Add --headless to Project Settings › Editor › Run › Main Run Args to run games without a window (everything except screenshot works). The repository's own CI runs a headless editor and headless games on Linux for the end-to-end tests — see .github/workflows/ci.yml.

Development

scripts/test-godot-unit.sh                   # GDScript unit tests (headless)
cd server && npm run typecheck && npm test   # TypeScript unit tests
npm run build && npm run test:e2e            # end-to-end against a real headless editor + game
E2E_GAME_WINDOW=1 npm run test:e2e           # same, with game windows (enables screenshot checks)

Limitations

• One MCP client per editor at a time (a new connection replaces the old one).
• script_write validates GDScript only; a script that references its own new class_name may compile-check slightly less strictly.
• C# projects are not supported yet.

License

MIT © OSHO