beckettlab/beckett-godot-mcp

> *Stop waiting for Godot.*
**Beckett** is a **zero-sidecar** Model Context Protocol (MCP) server embedded directly in the **Godot 4** editor as a GDScript EditorPlugin. AI agents (Claude and others) drive the editor over HTTP — no Node/Python bridge, no second process, no cloud.
This repository is the free, **MIT-licensed Lite edition**: the complete **inspect → author → run → SEE** dev loop (56 tools), for **GDScript *and* C#**. The AI can now *watch your running game* on the free tier: screenshot it, read the live remote scene tree and node state, poll performance monitors, and tail the game's logs. The paid **Full** edition makes the AI the *playtester* (it drives input, clicks 2D/3D and UI, and asserts the results), plus a test runner, animation tools, scatter_nodes, background exports, project-wide analysis, and 46 knowledge packs. See What Full adds.
**Lite: the AI sees your game. Full: the AI playtests it.**
Demo
Why
Existing Godot MCP servers either shell out to the CLI (can't play the game, screenshot, or inspect runtime) or run a Node/Python **sidecar** that relays to a thin in-editor addon. This one makes the **addon itself the MCP server**, and exposes **reflection-generic** tools that work on *any* class via ClassDB — instead of hundreds of hand-coded per-domain wrappers (an anti-pattern: LLMs degrade past ~40 tools).
Highlights
- **Zero-sidecar** — TCPServer HTTP/JSON-RPC server polled on the editor main thread. No marshalling, nothing extra to install beyond the addon.
- **The AI sees your game (free)** — screenshot the running game, read the live remote scene tree (get_remote_tree / find_nodes / wait_for_node), read live node state (runtime_get_property / monitor_properties), poll get_performance_monitors, and tail game_logs with stack traces. The free tier can watch and diagnose the running game; **Full closes the loop by driving input and asserting the result.**
- **GDScript and C#, one addon, zero sidecar** — the C#/.NET dev loop is free too: build_csharp runs a dotnet build compile-check that returns structured file:line:col + CS-code diagnostics (safe while the editor is open, no new dependency beyond the .NET SDK a C# project already needs), write_script is .cs-aware, and reflection surfaces your C# [GlobalClass] types just like GDScript class_name.
- **Reflection-first + discovery** — find_classes / describe_class / find_methods make the whole engine surface searchable; describe_object / set_property / call_method then drive any Node / Resource / Object. Reaches TileMap, GPUParticles, AnimationTree, NavMesh, shaders… with no per-domain code.
- **GDScript dev-loop with validate-before-write** — write_script / script_patch parse the code first and refuse to write what doesn't compile (closing the #1 AI-on-Godot failure: hallucinated GDScript). Godot's edge over UE: reload needs no compile step.
- **Undoable authoring** — every scene/node mutation goes through EditorUndoRedoManager (atomic + undoable); batch_execute rolls a whole batch back on failure.
- **One-step install** — enabling the plugin auto-starts the server and writes .mcp.json, so claude/Cursor connects with zero hand-editing (no Node.js to install — the competitor needs it just to try).
- **Security**: localhost-only, with exact Host and Origin checks (anti DNS-rebind), a per-project token for new projects, file reads confined to the project, and read-only / allowlist / confirm-destructive gates; auto-start is opt-out (beckett/autostart=false). SECURITY.md says what is protected, what is not, and how to report a problem.
- **Run → see loop** — play_scene → wait_until → logs_read → screenshot / get_remote_tree → fix: launch the game, tail its output and errors, then look at the running frame and live scene tree to diagnose. (Full closes the loop autonomously: the AI drives the game and asserts.) Plus **MCP Resources + Prompts**.
- **Dock panel** — status, one-click Start/Stop, copy-client-config, and an **AI-effort slider** (1–4 in Lite; L4 = *See*) that caps how many tools are advertised: cheaper model context when you only need a slice. **Applies live, no reconnect** — the server pushes notifications/tools/list_changed over its SSE stream and list-changed-aware clients (Claude Code, Cursor, …) re-fetch on the spot.