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 xobotyi/cc-foundry --skill cssgit clone --depth 1 https://github.com/xobotyi/cc-foundryWrote 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/xobotyi/cc-foundry/css)<a href="https://agentmods.dev/skills/xobotyi/cc-foundry/css"><img src="https://agentmods.dev/badge/skills/xobotyi/cc-foundry/css/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/xobotyi/cc-foundry/css"><img src="https://agentmods.dev/badge/skills/xobotyi/cc-foundry/css.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 | $0.00055 | $0.03741 |
| Opus 5.5 | $0.00022 | $0.01496 |
| Sonnet 5.5 | $0.00011 | $0.00748 |
| Haiku 4.5 | $0.00006 | $0.00374 |
Grade B, and why
css scanned grade B with 1 finding 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.
Strips warnings and disclaimersmediumAnti-refusal
Omitting safety caveats hides risk from the user and is a common jailbreak preamble.
- Don't lecture or quote the rule — state what's wrong and how to fix it. How it starts
The opening of the file, as written. The whole thing — 314 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CSS
Predictability is the highest CSS virtue. If your styles require !important to work, restructure the cascade.
CSS rewards explicit, low-specificity selectors and intentional cascade ordering. Prefer boring, readable patterns over clever one-liners.
References
- Layout — [
${CLAUDE_SKILL_DIR}/references/layout.md]: Flex shorthand values, grid details (subgrid, implicit rows, alignment), layout patterns - Modern CSS — [
${CLAUDE_SKILL_DIR}/references/modern-css.md]: Extended modern CSS patterns and examples - SCSS — [
${CLAUDE_SKILL_DIR}/references/scss.md]:@forwardpatterns, module configuration, built-in modules, file organization - Responsive — [
${CLAUDE_SKILL_DIR}/references/responsive.md]: Extended responsive design patterns and examples - Methodologies — [
${CLAUDE_SKILL_DIR}/references/methodologies.md]: Methodology patterns and architecture details
Selectors and Specificity
- Single class selectors by default — keep specificity flat at 0-1-0
- Never use ID selectors for styling — IDs are for anchors and JS hooks
- Never qualify classes with elements —
.errornotdiv.error - Max nesting depth: 3 levels — deeper nesting couples CSS to DOM structure
- Avoid
!important— use cascade layers or restructure selectors instead; only valid use is in a low-priority reset layer for truly essential styles - Use
:where()to zero-out specificity when needed —:where(.card) .titlehas 0-0-1 specificity - Use
:is()with awareness — it takes the highest specificity of its arguments - Flatten nested selectors in SCSS — ability to nest does not mean you should
Layout Systems
Choosing Flexbox vs Grid
| Use Case | System |
|---|---|
| One-dimensional flow (row or column) | Flexbox |
| Two-dimensional layout (rows AND columns) | Grid |
| Content-driven sizing | Flexbox |
| Layout-driven sizing | Grid |
| Component internals (nav items, card content) | Flexbox |
| Page-level structure, complex arrangements | Grid |
| Items need to wrap naturally | Flexbox |
| Precise placement on named lines/areas | Grid |
What ships with it
6 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.
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 First seen · 314 lines · 55 tokens per session scan B e3f8423898ed
css is a skill published in the GitHub repository xobotyi/cc-foundry (22 stars, last pushed 7d ago), licensed MIT. It adds 55 tokens to every session and 3,741 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it B with 1 finding (strips warnings and disclaimers). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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