design-system

design-system is a skill for Claude Code, OpenCode from TraftG/opencode-game-studio. It costs 45 tokens per session (4,161 once invoked), scanned A, original, MIT.

A guided writing workflow for a game design document covering one game system, such as combat. It reads the wider game concept and related systems before helping write the document section by section.

In plain words
What is it for?
Use it to author a system design document, cross-reference related systems, and save the work incrementally in the project documentation.
Why use it?
It keeps a system's design connected to the rest of the game and exposes missing context or dependencies while the document is being written.

Skill for Claude CodeOpenCode

Written for Claude Code and OpenCode: allowed-tools in frontmatter, but also installed under .opencode/. Also seen: names the AskUserQuestion tool; mentions OpenCode.

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/traftg/opencode-game-studio/design-system
Any agent
npx skills add TraftG/opencode-game-studio --skill design-system
Clone the repo
git clone --depth 1 https://github.com/TraftG/opencode-game-studio

Made for: Claude Code, OpenCode.

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 design-system

README.md
[![agentmods](https://agentmods.dev/badge/skills/traftg/opencode-game-studio/design-system.svg)](https://agentmods.dev/skills/traftg/opencode-game-studio/design-system)
Your own site
<a href="https://agentmods.dev/skills/traftg/opencode-game-studio/design-system"><img src="https://agentmods.dev/badge/skills/traftg/opencode-game-studio/design-system.svg" alt="Measured on agentmods" height="20"></a>
Per session 45 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 4,161 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 $0.00045 $0.04161
Opus 5 $0.00023 $0.02080
Sonnet 5 $0.00009 $0.00832
Haiku 4.5 $0.00005 $0.00416

Measured 2d ago against content hash ad9c1f18cc7e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

design-system 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.

Origin

Copies of this mod

2 near-identical copies found in the catalogue:

.opencode/skills/design-system/SKILL.md · 497 lines

How it starts

The opening of the file, as written. The whole thing — 497 lines — stays where its author put it; the contents beside it link to each section on GitHub.

When this skill is invoked:

1. Parse Arguments & Validate

A system name argument is required. If missing, fail with:

"Usage: /design-system <system-name> — e.g., /design-system combat-system Run /map-systems first to create the systems index, then use this skill to write individual system GDDs."

Normalize the system name to kebab-case for the filename (e.g., "combat system" becomes combat-system).


2. Gather Context (Read Phase)

Read all relevant context before asking the user anything. This is the skill's primary advantage over ad-hoc design — it arrives informed.

2a: Required Reads

  • Game concept: Read design/gdd/game-concept.md — fail if missing:

    "No game concept found. Run /brainstorm first."

  • Systems index: Read design/gdd/systems-index.md — fail if missing:

    "No systems index found. Run /map-systems first to map your systems."

  • Target system: Find the system in the index. If not listed, warn:

    "[system-name] is not in the systems index. Would you like to add it, or design it as an off-index system?"

2b: Dependency Reads

From the systems index, identify:

  • Upstream dependencies: Systems this one depends on. Read their GDDs if they exist (these contain decisions this system must respect).
  • Downstream dependents: Systems that depend on this one. Read their GDDs if they exist (these contain expectations this system must satisfy).

For each dependency GDD that exists, extract and hold in context:

  • Key interfaces (what data flows between the systems)
  • Formulas that reference this system's outputs
  • Edge cases that assume this system's behavior
  • Tuning knobs that feed into this system

2c: Optional Reads

  • Game pillars: Read design/gdd/game-pillars.md if it exists
  • Existing GDD: Read design/gdd/[system-name].md if it exists (resume, don't restart from scratch)
  • Related GDDs: Glob design/gdd/*.md and read any that are thematically related (e.g., if designing "status-effects", also read "combat-system" even if it's not a direct dependency)

Read the full file on GitHub · 497 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. 2d ago First seen · 497 lines · 45 tokens per session scan A ad9c1f18cc7e

Subscribe to this mod's changes

design-system is a skill published in the GitHub repository TraftG/opencode-game-studio (38 stars, last pushed 4mo ago), licensed MIT. It adds 45 tokens to every session and 4,161 once invoked, about $0.0002 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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