Unity Development Loop Agent Skill

Run Unity runtime development loops with gameplay-focused implementation and validation.

Context cost
3.6k tokensestimated from the bundle, loaded when it triggers
Bundle
3 files · 14.3 kBtext throughout, nothing executable
Licence
MITthe author’s own terms
Last change
—v0.3.0
Servers it uses
Noneruns standalone

What it does

Run Unity runtime development loops with gameplay-focused implementation and validation. Use when the user asks to iterate on runtime behavior, reproduce and fix a gameplay bug, measure Editor operation latency, or implement a Unity-side flow until acceptance criteria are met. Do not use for `.inputactions` authoring, read-only inspection, or Rust CLI-only work.

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

gamedevunity

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md6.6 kB · preview
--- name: unity-development-loop compatibility: Requires unity-cli connected to a Unity Editor that supports Play Mode control, runtime input simulation, UI automation, and editor diagnostics. allowed-tools: Bash(unity-cli:*), Read, Grep, Glob metadata: author: akiojin version: 0.3.0 category: testing triggers: - runtime - gameplay - iterate - acceptance - latency - benchmark ---
19# Unity Development Loop
20
21With --output json, results use {success, command, data, errors, warnings}. Check the exit status and envelope success first; tool-result fields in this skill are relative to data. Read failure codes from errors[0].code; see unity-cli-usage for exit-code recovery.
22
23Run Unity-side development as short, acceptance-driven loops.
24This skill chooses the smallest next change, the narrowest runtime check, and the lightest evidence set that can prove or disprove the current hypothesis.
25
26## Use When
27
28- The user wants to implement and verify a Unity gameplay, input, or UI scenario.
29- The task needs a repeatable loop of Unity-side code changes, Play Mode execution, evidence capture, and runtime confirmation.
30- The user asks to iterate on a runtime bug until acceptance criteria are satisfied.
31- The request needs screenshots, short video, console inspection, or profiler data as part of Unity runtime validation.
32- The user wants to measure Editor operation latency or check performance budgets in a unity-cli source checkout.
33
34## Do Not Use When
35
36- The task is authoring .inputactions assets instead of validating runtime behavior. Use unity-input-system.
37- The task is read-only code or scene investigation with no planned change. Use the relevant inspection skill.
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md905 words
Files3
LicenceMIT
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈200
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
3,375
on trigger
The instruction body and 2 supporting files, read only when the skill fires.
1.8%
of a 200k window
Ten skills this size would take about 18% of the window before you open a file.
050k100k150k200k context window

3.6k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Middling. Fine to keep on in a project where you use it weekly, worth unloading in one where you never do.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md asks for Bash, which can write files and reach the network alike, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

The allowed-tools line of this skill’s own SKILL.md asks for Bash, which could do either, so neither is ruled out. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

3 files, 14.3 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md6.6 kB
  • references/development-loop-playbook.md5.5 kB
  • references/runtime-checklist.md2.2 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 3 files you can review in full before installing. The MIT licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# Unity Development Loop · 3.6k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/unity-development-loop/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/unity-development-loop" ] && { [ ! -e .claude/skills/unity-development-loop ] || { mv .claude/skills/unity-development-loop "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/unity-development-loop" .claude/skills/ && echo "Installed .claude/skills/unity-development-loop"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add akiojin/unity-development-loop

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/unity-development-loop/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/unity-development-loop/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/unity-development-loop" ] && { [ ! -e ~/.claude/skills/unity-development-loop ] || { mv ~/.claude/skills/unity-development-loop "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/unity-development-loop" ~/.claude/skills/ && echo "Installed ~/.claude/skills/unity-development-loop" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/unity-development-loop/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Version0.3.0
Publishedno release date on file
PriceFree
Referenceakiojin/unity-development-loop

Versions

v0.3.0 is what is on the shelf; no release here carries a date. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

v0.3.0
  • No earlier releases have been published to the marketplace.
Pinning

The install command always fetches the release that is current the day you run it — v0.3.0 today — and cannot ask for an earlier one. The copy on your disk does not change until you run it again.

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