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.
npx skills add fcsouza/agent-skills --skill foundry-vtt-system-devgit clone --depth 1 https://github.com/fcsouza/agent-skillsWrote 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.
[](https://agentmods.dev/skills/fcsouza/agent-skills/foundry-vtt-system-dev)<a href="https://agentmods.dev/skills/fcsouza/agent-skills/foundry-vtt-system-dev"><img src="https://agentmods.dev/badge/skills/fcsouza/agent-skills/foundry-vtt-system-dev/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.
<a href="https://agentmods.dev/skills/fcsouza/agent-skills/foundry-vtt-system-dev"><img src="https://agentmods.dev/badge/skills/fcsouza/agent-skills/foundry-vtt-system-dev.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00212 | $0.13165 |
| Opus 5.5 | $0.00085 | $0.05266 |
| Sonnet 5.5 | $0.00042 | $0.02633 |
| Haiku 4.5 | $0.00021 | $0.01316 |
Grade A, and why
foundry-vtt-system-dev 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 1mo 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.
The source is not reproduced here
Licensed GPL-3.0
The repository is licensed GPL-3.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.
What ships with it
38 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.
- boilerplate/actor.mjs 2.1 KB runs code
- boilerplate/config.mjs 919 B runs code
- boilerplate/data/_module.mjs 190 B runs code
- boilerplate/data/character-data.mjs 2.5 KB runs code
- boilerplate/data/npc-data.mjs 1.5 KB runs code
- boilerplate/data/spell-data.mjs 1.3 KB runs code
- boilerplate/data/weapon-data.mjs 748 B runs code
- boilerplate/documents/_module.mjs 90 B runs code
- boilerplate/item.mjs 1.4 KB runs code
- boilerplate/main.mjs 6.9 KB runs code
- boilerplate/migration.mjs 2.8 KB runs code
- boilerplate/settings.mjs 542 B runs code
- boilerplate/sheets/_module.mjs 102 B runs code
- boilerplate/sheets/character-sheet.mjs 3.9 KB runs code
- boilerplate/sheets/item-sheet.mjs 1.3 KB runs code
- boilerplate/styles/my-system.less 771 B
- boilerplate/styles/v2/apps.less 1.2 KB
- boilerplate/styles/v2/character.less 1.4 KB
- boilerplate/styles/v2/chat.less 1.5 KB
- boilerplate/styles/v2/items.less 980 B
- boilerplate/styles/v2/sheets.less 2.3 KB
- boilerplate/styles/v2/typography.less 437 B
- boilerplate/styles/variables/base.less 1.3 KB
- boilerplate/styles/variables/dark.less 647 B
- boilerplate/styles/variables/light.less 781 B
- boilerplate/system.json 2.1 KB
- boilerplate/templates/actor/character-sheet.hbs 4.1 KB
- boilerplate/templates/item/item-sheet.hbs 808 B
- references/actor-item-classes.md 19 KB
- references/advanced-system-features.md 24 KB
- references/character-creation.md 13 KB
- references/combat-initiative.md 14 KB
- references/data-migration.md 17 KB
- references/dice-system.md 20 KB
- references/production-patterns.md 18 KB
- references/styling-and-themes.md 19 KB
- references/system-manifest.md 18 KB
- templates/system-checklist.md 7.0 KB
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.
- 1mo ago Changed · +149 lines · +52 tokens per session bfdd7893b95b
- 1mo ago Changed · -1 lines af3d0191f24a
- 1mo ago First seen · 825 lines · 160 tokens per session scan A 0d2c405fbfff
foundry-vtt-system-dev is a skill published in the GitHub repository fcsouza/agent-skills (22 stars, last pushed 6d ago), licensed GPL-3.0. It adds 212 tokens to every session and 13,165 once invoked, about $0.0008 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.
Other skills, from other repositories
playtest-report
Structured playtest report template, or turn existing playtest notes into structured feedback.
godot-signals-groups
Build event-driven, decoupled Godot 4.7 gameplay with signals and node groups: declare and emit custom signals, connect with Callables (incl. bind/one-shot), and broadcast to many nodes via groups and callgroup. Use when wiring node communication in a Godot project, replacing tight references with signals…
motion
Reconstruct a skeleton from calibrated mesh projections and sequential VLM joint annotations, then fit joints and skin weights. Generate motion from joint-position trajectories, rhythm and contact constraints through IK; refine bone orientation against the action, then export, retarget and validate on the target mesh.
unity-addressables
Manage Addressables groups, entries, profiles and content builds (com.unity.addressables, reflection-based).
threejs-exposure-color-grading
Build a measured exposure and grading path in Three.js. Use for a 64x36 encoded luminance meter, asynchronous readback, weighted log-average exposure, asymmetric adaptation, single tone-map ownership, and a generated 32-cube post-tone-map LUT.
unity-manual-component
Manually add, configure, reorder, and copy components on GameObjects using Unity Editor UI. For one-off Inspector workflows that do not need REST automation.