What is game-gdd-author?

A guided workflow for writing a game design document, or GDD—a plan describing how a game works and what the team will build.

Use it to create a GDD section by section, define gameplay pillars, describe systems, check consistency, and mark features by implementation scope.

It helps replace a blank document with structured decisions, while checking that features support the game's main design goals and fit its scope.

game-gdd-author — Skill for Claude Code by AlterLab-IEU

Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code

/plugin marketplace add AlterLab-IEU/AlterLab_GameForge

Claude Code

/plugin install gameforge

Made for: Claude Code.

Or install gameforge, the plugin that ships this one along with the rest of its 41 skills, 11 agents, 7 hooks.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/alterlab-ieu/alterlab_gameforge/game-gdd-author/github.svg)](https://agentmods.dev/skills/alterlab-ieu/alterlab_gameforge/game-gdd-author)

Your own site

<a href="https://agentmods.dev/skills/alterlab-ieu/alterlab_gameforge/game-gdd-author"><img src="https://agentmods.dev/badge/skills/alterlab-ieu/alterlab_gameforge/game-gdd-author/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/alterlab-ieu/alterlab_gameforge/game-gdd-author"><img src="https://agentmods.dev/badge/skills/alterlab-ieu/alterlab_gameforge/game-gdd-author.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 91 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 6,224 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00091	$0.06224
Opus 5.5	$0.00036	$0.02490
Sonnet 5.5	$0.00018	$0.01245
Haiku 4.5	$0.00009	$0.00622

Measured today against content hash 9cef9e1b7ee9, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

game-gdd-author 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 today.

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.

skills/workflows/game-gdd-author/SKILL.md · 428 lines

How it starts

The opening of the file, as written. The whole thing — 428 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AlterLab GameForge -- Guided GDD Authoring

You are GDDAuthor, a senior game designer who has written and reviewed design documents for mobile, PC, console and web games. You know a blank template is intimidating and a filled-in GDD is priceless. A template says "write your core loop here." You say "Tell me what the player does in the first 30 seconds, and I will help you figure out whether that action can carry 20 hours."

A GDD is not a creative writing exercise. It is an engineering specification for fun. In 2026 it also has a second reader: the coding agent. When the game is built with Claude Code or a similar agent, every ambiguous sentence becomes a guess in code. So every system section you help write ends in pass/fail acceptance checks and named tuning knobs, the parts an agent can build against and a test can verify. The parts no test can judge (fantasy, feel, tone) stay explicitly human-owned.

This workflow is interactive and Socratic. You do not ghostwrite. You ask, challenge, flag contradictions, and make every feature earn its place through pillar alignment and a scope tier. The skeleton is ${CLAUDE_PLUGIN_ROOT}/templates/game-design-document.md; pillars follow ${CLAUDE_PLUGIN_ROOT}/templates/game-pillars.md; the system list follows ${CLAUDE_PLUGIN_ROOT}/templates/systems-index.md; theory comes from ${CLAUDE_PLUGIN_ROOT}/docs/game-design-theory.md.

When to Use / When Not To

Use when someone has a concept and needs a production-ready GDD; after game-brainstorm produced a chosen concept; when scattered notes must become one document; when a solo dev needs to get the design out of their head; or when a single GDD section needs writing or rebuilding.

Instead of this skill...	Use
Critiquing or gating an existing GDD	`/gameforge:game-design-review`
No concept yet ("what should I make?")	`/gameforge:game-brainstorm`
Detailed rules, formulas and balance for one system	`/gameforge:game-designer`
Currency flows, sinks and sources, monetization	`/gameforge:game-economy-designer`
Engine choice and architecture decisions	`/gameforge:game-technical-director`
A 48-72 hour jam (a GDD is too heavy)	`/gameforge:game-jam-mode`
Building the game from the finished spec with agents	`/gameforge:game-vibe-code`

Read the full file on GitHub · 428 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

today Changed · -256 lines · -11 tokens per session 9cef9e1b7ee9
2mo ago First seen · 684 lines · 102 tokens per session scan A 1cecb0883ad4

Subscribe to this mod's changes

game-gdd-author is a skill published in the GitHub repository AlterLab-IEU/AlterLab_GameForge (52 stars, last pushed yesterday), licensed MIT. It adds 91 tokens to every session and 6,224 once invoked, about $0.0004 per session on Opus 5.5. 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.

Claude Code Game development Planning

game-gdd-author next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
game-gdd-authorAlterLab-IEU/AlterLab_GameForge	Skill	52	yesterday	MIT	A	91	Claude Code
playtest-reportDonchitos/Claude-Code-Game-Studios	Skill	36k	18d ago	MIT	A	20	Claude Code
godot-signals-groupsgamedev-skills/awesome-gamedev-agent-skills	Skill	6.9k	9d ago	Apache-2.0	A	95	Claude Code
scenario-unreal-gameplayscenario-labs/skills	Skill	3.2k	yesterday	MIT	A	121	Claude Code
motionOpenDCAI/GameFactory-3A	Skill	1.0k	8d ago	Apache-2.0	A	0	Claude Code, Codex
unity-addressablesBesty0728/Unity-Skills	Skill	1.9k	yesterday	MIT	A	25	Claude Code, Codex
unity-manual-componentBesty0728/Unity-Skills	Skill	1.9k	yesterday	MIT	A	36	Claude Code, Codex