script-update-or-create

script-update-or-create is a skill for Claude Code from IvanMurzak/Unity-MCP. It costs 80 tokens per session (568 once invoked), scanned A, original, Apache-2.0.

A tool for creating or replacing a C# script file after checking that its code has valid C# syntax. It refreshes Unity's project files and reports compilation errors after Unity recompiles.

In plain words
What is it for?
Use it to create Unity scripts, update existing C# files, and detect syntax or compilation problems.
Why use it?
It reduces the risk of overwriting a script with malformed code and gives feedback from Unity's compilation step.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

About the project

Unity-MCP connects AI coding agents to the Unity game engine through MCP, letting them work with the Unity Editor and running games. It is used by game developers to generate code, automate development and testing, debug projects, and add AI-driven behavior to games. The catalogue entries provide skills, instructions, an MCP integration, and settings for operating this workflow.

IvanMurzak/Unity-MCP · 4,177 stars · on GitHub · ai-game.dev

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 skills/ivanmurzak/unity-mcp/script-update-or-create
Any agent
npx skills add IvanMurzak/Unity-MCP --skill script-update-or-create
Clone the repo
git clone --depth 1 https://github.com/IvanMurzak/Unity-MCP

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for script-update-or-create

README.md
[![agentmods](https://agentmods.dev/badge/skills/ivanmurzak/unity-mcp/script-update-or-create.svg)](https://agentmods.dev/skills/ivanmurzak/unity-mcp/script-update-or-create)
Your own site
<a href="https://agentmods.dev/skills/ivanmurzak/unity-mcp/script-update-or-create"><img src="https://agentmods.dev/badge/skills/ivanmurzak/unity-mcp/script-update-or-create.svg" alt="Measured on agentmods" height="20"></a>
Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 568 The whole file, excluding the scripts and references it only reads on demand.
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 5.1 $0.00080 $0.00568
Opus 5 $0.00040 $0.00284
Sonnet 5 $0.00016 $0.00114
Haiku 4.5 $0.00008 $0.00057

Measured 2d ago against content hash 8d30196b0491, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

script-update-or-create 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 2d ago.

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.

Unity-MCP-Plugin/.claude/skills/script-update-or-create/SKILL.md · 78 lines

What it actually says

Script / Update or Create

Updates or creates script file with the provided C# code. Does AssetDatabase.Refresh() at the end. Provides compilation error details if the code has syntax errors. Use 'script-read' tool to read existing script files first.

Inputs

  • filePath — required .cs path.
  • content — C# source. MUST pass ScriptUtils.IsValidCSharpSyntax.
  • requestId — required for the processing/delivered-later contract.

Behavior

Creates any missing parent directories, writes the file, then calls AssetDatabase.Refresh and schedules a post-compilation notification so the final response is delivered after Unity finishes the recompile.

How to Call

unity-mcp-cli run-tool script-update-or-create --input '{
  "filePath": "string_value",
  "content": "string_value"
}'

For complex input (multi-line strings, code), save the JSON to a file and use:

unity-mcp-cli run-tool script-update-or-create --input-file args.json

Or pipe via stdin (recommended):

unity-mcp-cli run-tool script-update-or-create --input-file - <<'EOF'
{"param": "value"}
EOF

Troubleshooting

If unity-mcp-cli is not found, either install it globally (npm install -g unity-mcp-cli) or use npx unity-mcp-cli instead. Read the /unity-initial-setup skill for detailed installation instructions.

Input

Name Type Required Description
filePath string Yes The path to the file. Sample: "Assets/Scripts/MyScript.cs".
content string Yes C# code - content of the file.

Input JSON Schema

{
  "type": "object",
  "properties": {
    "filePath": {
      "type": "string"
    },
    "content": {
      "type": "string"
    }
  },
  "required": [
    "filePath",
    "content"
  ]
}

Output

This tool does not return structured output.

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. 2d ago First seen · 78 lines · 80 tokens per session scan A 8d30196b0491

Subscribe to this mod's changes

script-update-or-create is a skill published in the GitHub repository IvanMurzak/Unity-MCP (4,177 stars, last pushed yesterday), licensed Apache-2.0. It adds 80 tokens to every session and 568 once invoked, about $0.0004 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 2026-09-03.

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