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 Phelan164/codex-howto --skill build-frontendgit clone --depth 1 https://github.com/Phelan164/codex-howtoWrote 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/phelan164/codex-howto/build-frontend)<a href="https://agentmods.dev/skills/phelan164/codex-howto/build-frontend"><img src="https://agentmods.dev/badge/skills/phelan164/codex-howto/build-frontend.svg" alt="Measured on agentmods" 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 | $0.00057 | $0.00294 |
| Opus 5 | $0.00028 | $0.00147 |
| Sonnet 5 | $0.00011 | $0.00059 |
| Haiku 4.5 | $0.00006 | $0.00029 |
Grade A, and why
build-frontend 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 8d 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.
What it actually says
Build Frontend
Domain contract
- Preserve the project’s framework, styling system, and component conventions.
- Do not invent API response fields or silently change backend contracts.
- Do not replace an established design system with custom one-off styling.
- Define loading, empty, error, success, and disabled states that the changed flow can reach.
- Keep semantic HTML, keyboard navigation, focus behavior, labels, and contrast in scope.
- Avoid speculative shared abstractions for a single component.
- Treat screenshots and mockups as visual references, not proof of interaction behavior.
- Do not claim visual verification unless the UI was rendered or inspected.
Execute and verify
Read references/verification.md for UI, accessibility, responsive, and browser verification. Load it when the task changes rendered behavior or interaction.
Reuse existing components and tokens, implement the smallest coherent change, and prove behavior at the lowest useful layer. Prefer:
component test → feature test → type/lint → build → visual/interaction check
If a command cannot run, report the exact blocker and what remains unverified.
What ships with it
2 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.
- 8d ago First seen · 32 lines · 57 tokens per session scan A 8c34e89a05f5
build-frontend is a skill published in the GitHub repository Phelan164/codex-howto (3 stars, last pushed 3d ago), licensed MIT. It adds 57 tokens to every session and 294 once invoked, about $0.0003 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 2026-08-31.
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