agentmods.dev

mcp-unity AGENTS.md

Developer guidance for MCP Unity, which lets AI tools control parts of the Unity Editor. Unity is software for building games and interactive 3D applications; MCP is a way for AI clients to call tools and access resources.

In plain words
What is it for?
Use it when adding, changing, or debugging tools and resources that connect an MCP client to the Unity Editor.
Why use it?
It explains how the Node server communicates with Unity, where settings live, and which names and execution rules must stay consistent.

Instructions file for CodexOpenCode

1.9k 5d ago A scan 2,498 tokens original MIT
View the source file CoderGamester/mcp-unity
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add instructions/codergamester/mcp-unity/agents-md
Clone the repo
git clone --depth 1 https://github.com/CoderGamester/mcp-unity

Made for: Codex, OpenCode.

Per session 2,498 This file is loaded in full into every session.
When invoked 2,498 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.02498 $0.02498
Opus 5 $0.01249 $0.01249
Sonnet 5 $0.00500 $0.00500
Haiku 4.5 $0.00250 $0.00250

Measured yesterday against content hash 35756cdbf04f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

mcp-unity AGENTS.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

AGENTS.md · 184 lines

How it starts

The opening of the file, as written. The whole thing — 184 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCP Unity — AI Agent Guide (MCP Package)

Purpose (what this repo is)

MCP Unity exposes Unity Editor capabilities to MCP-enabled clients by running:

  • Unity-side “client” (C# Editor scripts): a WebSocket server inside the Unity Editor that executes tools/resources.
  • Node-side “server” (TypeScript): an MCP stdio server that registers MCP tools/resources and forwards requests to Unity over WebSocket.

How it works (high-level data flow)

  • MCP client ⇄ (stdio / MCP SDK) ⇄ Node server (Server~/src/index.ts)
  • Node server ⇄ (WebSocket JSON-RPC-ish) ⇄ Unity Editor (Editor/UnityBridge/McpUnityServer.cs + McpUnitySocketHandler.cs)
  • Tool/Resource names must match exactly across Node and Unity (typically lower_snake_case).

Key defaults & invariants

  • Unity WebSocket endpoint: ws://localhost:8090/McpUnity by default.
  • Config file: ProjectSettings/McpUnitySettings.json (written/read by Unity; read opportunistically by Node).
  • Execution thread: Tool/resource execution is dispatched via EditorCoroutineUtility and runs on the Unity main thread. Keep synchronous work short; use async patterns for long work.

Repo layout (where to change what)

/
├── Editor/                       # Unity Editor package code (C#)
│   ├── Tools/                    # Tools (inherit McpToolBase)
│   ├── Resources/                # Resources (inherit McpResourceBase)
│   ├── UnityBridge/              # WebSocket server + message routing
│   ├── Services/                 # Test/log services used by tools/resources
│   └── Utils/                    # Shared helpers (config, logging, workspace integration)
├── Server~/                      # Node MCP server (TypeScript, ESM)
│   ├── src/index.ts              # Registers tools/resources/prompts with MCP SDK
│   ├── src/tools/                # MCP tool definitions (zod schema + handler)
│   ├── src/resources/            # MCP resource definitions
│   └── src/unity/mcpUnity.ts      # WebSocket client that talks to Unity

Read the full file on GitHub · 184 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 184 lines · 2,498 tokens per session scan A 35756cdbf04f

Subscribe to this mod's changes

mcp-unity AGENTS.md is an instructions file published in the GitHub repository CoderGamester/mcp-unity (1,881 stars, last pushed 5d ago), licensed MIT. It adds 2,498 tokens to every session, about $0.0125 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Data and AIDebuggingGame developmentcopilotcursorgame-developmentmcpunityunity-package
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