foundry-vtt-module-dev

foundry-vtt-module-dev is a skill for Claude Code, Codex from fcsouza/agent-skills. It costs 178 tokens per session (9,126 once invoked), scanned A, original, GPL-3.0.

A guide for building and maintaining Foundry VTT modules, which add features or integrations to the Foundry virtual tabletop.

In plain words
What is it for?
Use it to create modules, build sheets and dialogs, add settings and event hooks, communicate between clients, and extend the game canvas.
Why use it?
It provides instructions for common module work in Foundry VTT version 13 and later, reducing the need to work out the platform details from scratch.

Skill for Claude CodeCodex

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/fcsouza/agent-skills/foundry-vtt-module-dev
Any agent
npx skills add fcsouza/agent-skills --skill foundry-vtt-module-dev
Clone the repo
git clone --depth 1 https://github.com/fcsouza/agent-skills

Made for: Claude Code, Codex.

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 foundry-vtt-module-dev

README.md
[![agentmods](https://agentmods.dev/badge/skills/fcsouza/agent-skills/foundry-vtt-module-dev.svg)](https://agentmods.dev/skills/fcsouza/agent-skills/foundry-vtt-module-dev)
Your own site
<a href="https://agentmods.dev/skills/fcsouza/agent-skills/foundry-vtt-module-dev"><img src="https://agentmods.dev/badge/skills/fcsouza/agent-skills/foundry-vtt-module-dev.svg" alt="Measured on agentmods" height="20"></a>
Per session 178 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 9,126 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00178 $0.09126
Opus 5 $0.00089 $0.04563
Sonnet 5 $0.00036 $0.01825
Haiku 4.5 $0.00018 $0.00913

Measured 5d ago against content hash 5c6f02c3a3b4, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

foundry-vtt-module-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 5d ago.

The scan reads SKILL.md. This mod also ships 6 executable files (boilerplate/actor-sheet.mjs, boilerplate/main.mjs, boilerplate/rollup.config.mjs, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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/foundry-vtt-module-dev/SKILL.md · 835 lines

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.

Read it on GitHub

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. 5d ago First seen · 835 lines · 178 tokens per session scan A 5c6f02c3a3b4

Subscribe to this mod's changes

foundry-vtt-module-dev is a skill published in the GitHub repository fcsouza/agent-skills (20 stars, last pushed 4d ago), licensed GPL-3.0. It adds 178 tokens to every session and 9,126 once invoked, about $0.0009 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 2026-08-30.

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