Guide · Agent skill
How to use the Asset Spec Writer agent skill (asset-spec)
Updated · written with AI from the project's own documentation and checked against our catalogue data
The Asset Spec Writer (skill name asset-spec) is an agent skill for Claude Code and compatible SKILL.md runtimes. It reads a game's design documents and art bible, builds a checklist of visual assets such as characters, enemies, buildings, UI screens and VFX, and writes a detailed spec for each one, including text prompts you can give to an AI image generator. This guide explains what the skill does, how to install it, how to trigger it with plain requests, and what it needs before it will run.
Asset Spec WriterDonchitos/Claude-Code-Game-Studios · MIT Download the skill Quick start
- 1Download the ZIP. Get the asset-spec ZIP from the skill's page on this site.
- 2Install the skill folder. Unzip it into ~/.claude/skills/ for personal use, or into your project's .claude/skills/ folder. Alternatively, upload the ZIP under Settings → Capabilities → Skills in the Claude apps.
- 3Prepare the art bible. Make sure design/art/art-bible.md exists, and that your design docs are in design/gdd/.
- 4Run the inventory. Ask the agent to build the asset inventory, or run /asset-spec with no argument if design/assets/entity-inventory.md is missing.
- 5Review and approve. Check the proposed list of characters, enemies, screens and VFX, then approve it so the skill writes design/assets/entity-inventory.md.
- 6Spec one item. Run asset-spec with system:, level: or character: and a name, choosing a review mode if you want one.
- 7Check the prompts. Read the generated prompts and specs against your art bible before using them in any image generator.
What the asset-spec skill makes the agent do
An agent skill is a folder containing a SKILL.md file that gives an AI agent a set of instructions, tools and rules for one kind of task. When this skill is active, the agent works in two stages. First it builds an entity and screen inventory, a master list of everything the game needs visually. Then it writes a spec for each item, anchored to the project's visual rules so the results stay consistent with each other.
The skill only produces text: specs and generation prompts. The material shown does not call an image API, so you will not get finished artwork from it. You take the prompts and use them with the image tool of your choice, with human review.
- Builds an inventory from the systems index, the Visual/Audio and UI requirement sections of game design documents, and the entity registry
- Writes per-asset specs for systems, levels or characters
- Reads the art bible first so specs follow the existing colour, shape and asset-standard rules
- Writes files under design/assets/ in your project
Install the Asset Spec Writer skill
You can install the skill in either of two ways. Download the ZIP from the skill's page on this site, then choose one of the options below.
For a personal setup available across your projects, unzip the download into ~/.claude/skills/. To limit it to one project, unzip it into that project's .claude/skills/ folder. In the Claude apps, you can instead upload the ZIP under Settings → Capabilities → Skills.
- Personal: ~/.claude/skills/
- Single project: .claude/skills/ inside the project folder
- Claude apps: Settings → Capabilities → Skills, then upload the ZIP
Check the requirements before you run it
The skill needs Claude Code or a compatible SKILL.md runtime, and Bash must be available, because the skill runs a bundled config script. Its allowed tools are Read, Glob, Grep, Write, Edit, Agent, AskUserQuestion and the restricted Bash call to hooks/yaml-helper.sh. The skill does not use the network, according to the material shown.
The project also needs files in known places. The skill fails without an art bible at design/art/art-bible.md. It also reads design documents in design/gdd/ and, when present, the entity registry at design/registry/entities.yaml. The skill calls its script through a relative path, ../../hooks/yaml-helper.sh from the skill folder, so that hooks folder must sit where that path resolves.
- Claude Code or a compatible SKILL.md runtime
- Bash available for the bundled yaml-helper.sh config script
- design/art/art-bible.md (required)
- Design docs in design/gdd/ (systems index and GDD sections)
- Optional: design/registry/entities.yaml and design/narrative/
Trigger the skill with natural requests
The skill accepts an argument in one of three target forms: system:<name>, level:<name> or character:<name>. You can add --review full, --review lean or --review solo. Names are normalised to kebab-case. Plain requests work as well, such as asking the agent to write asset specs for the combat system or to spec the forest level's visuals, since the agent can map these to the skill.
If you give no argument, the skill looks for design/assets/entity-inventory.md. If that file exists, it finds the first entity or screen marked Needed that has no spec yet and asks whether to spec it. If there is no inventory, it checks design/assets/asset-manifest.md. If neither exists, it starts the inventory flow.
- Spec a system: asset-spec system:combat
- Spec a level: asset-spec level:forest-ruins
- Spec a character: asset-spec character:ranger --review lean
- No argument: the skill picks the next unspecced item or builds the inventory
/asset-spec system:combatUnderstand review modes
Review mode controls which agents the skill spawns. In full mode, it spawns both art-director and technical-artist in parallel. In lean mode, it spawns art-director only and skips the technical constraint pass, which is faster. In solo mode, the main session writes specs from the art bible rules alone, which suits simple asset categories or quick work.
If you do not pass --review, the default follows your project's rigor setting: solo at minimal, lean at standard and full at full. A --review argument overrides this for one run only.
- full: art-director and technical-artist in parallel
- lean: art-director only, faster
- solo: no agents, main session only
Handle questions and missing files
The skill asks you questions through AskUserQuestion. How often it asks depends on your automation mode, defined in .claude/docs/automation-modes.md. Collaborative mode always asks, guided mode asks only on major decisions, and autonomous mode logs its choices and proceeds, except for categories listed under automation_always_ask.
If the art bible is missing, the skill stops and tells you to run /art-bible first. The exception is a project with design/game-brief.md but no art bible. Then the specs are anchored to the brief's Art & audio direction line, and the output says those rules are proposals, not constraints. Calling an external image generator always prompts you, whatever the automation mode.
- Missing art bible: run /art-bible first (unless a game brief exists)
- Inventory saved only after you approve it
- Live image generation is guarded and always asks first (not wired in today)
What people use it for
- Listing every UI screen and HUD element for a game before commissioning art
- Writing a consistent spec for each enemy type so artists or generators work from the same rules
- Producing a per-level list of background, prop and VFX assets from level design documents
- Drafting generation prompts for a solo developer who will review each image by hand
Frequently asked questions
How do I install the asset-spec agent skill?
Download the ZIP from this page and unzip it into ~/.claude/skills/ for personal use, or into a project's .claude/skills/ folder. In the Claude apps, you can upload the ZIP under Settings → Capabilities → Skills instead.
What do I need to run asset-spec?
You need Claude Code or a compatible SKILL.md runtime, with Bash available for the bundled config script. The project needs an art bible at design/art/art-bible.md, since the skill fails without it, plus design documents in design/gdd/.
Is the asset-spec skill free?
The listing states the licence is MIT. Check the licence file in the source repository for the full terms.
Why does asset-spec say there is no art bible?
The skill requires design/art/art-bible.md and stops if it is missing. Run /art-bible first to create one. If you only have design/game-brief.md, the skill can anchor specs to the brief's art direction line instead, and it will say those rules are proposals.
Does asset-spec generate images?
No. As described in the material shown, it writes specs and text prompts only and does not call an image API. You would copy the prompts into an image generator yourself, and any live generation would prompt for confirmation first.
How does asset-spec compare to writing art specs by hand?
The skill speeds up the inventory and first drafts, and keeps specs tied to your art bible and design docs. It still needs a person to check the output, because AI-generated prompts can drift from the intended style. The material shown does not compare it with other tools.
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Our verdict
Use asset-spec if you work in the Claude Code Game Studios setup, or you are a solo developer or art lead who has a game design doc and an art bible and needs a consistent list of visual assets with prompts. Skip it if you have no design document or art bible, since the skill is built to stop without them, or if you expect finished images, since it only writes text.
Download the skill