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 oaustegard/claude-skills --skill composing-htmlgit clone --depth 1 https://github.com/oaustegard/claude-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/oaustegard/claude-skills/composing-html)<a href="https://agentmods.dev/skills/oaustegard/claude-skills/composing-html"><img src="https://agentmods.dev/badge/skills/oaustegard/claude-skills/composing-html/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/oaustegard/claude-skills/composing-html"><img src="https://agentmods.dev/badge/skills/oaustegard/claude-skills/composing-html.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 3 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high System Prompt Leakage · line 170 Skill contains instructions that could directly expose system prompts, internal rules, or hidden instructions to users or external parties.Fix: Remove any instructions that reveal, print, or output system prompts or internal rules. System instructions should never be exposed to end users.
- high Prompt Injection · line 176 Hidden instructions were detected in comments or invisible text. These could contain malicious directives. Manual review is recommended.Fix: Audit all comments and invisible characters. Remove any instructions that direct the agent to perform unauthorized actions. Use plain, reviewable content.
- high System Prompt Leakage · line 216 Skill contains instructions that could directly expose system prompts, internal rules, or hidden instructions to users or external parties.Fix: Remove any instructions that reveal, print, or output system prompts or internal rules. System instructions should never be exposed to end users.
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 | $0.00151 | $0.03339 |
| Opus 5.5 | $0.00060 | $0.01336 |
| Sonnet 5.5 | $0.00030 | $0.00668 |
| Haiku 4.5 | $0.00015 | $0.00334 |
Grade A, and why
composing-html 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.
How it starts
The opening of the file, as written. The whole thing — 296 lines — stays where its author put it; the contents beside it link to each section on GitHub.
composing-html
Produce single-file HTML artifacts without hand-writing the page chrome. The
composer supplies <!DOCTYPE>, <head>, inlined CSS, base.js, design
tokens, masthead, and colophon. You supply a title and the body content.
The product is the chrome and inventory below — primitives you can drop into any artifact without re-deriving what a card, badge, or eyebrow looks like. Templates are shortcuts on top of this, useful when the same artifact shape repeats; see Templates near the end.
Default workflow: freeform
freeform gives you the whole chrome with one content slot — body_html —
for the page body. Reach for it first. Reach for a template only when the
structure repeats across artifacts (see Templates
near the end).
There are two ways to invoke it. Use the --set flow for anything with a
substantial body — it sidesteps the JSON-string escaping that bites
heredoc-style spec writing (newlines, quotes, </& inside multi-line
HTML).
Recommended: HTML in a file, metadata via --set
1. Write the body to a .html file directly (no JSON, no escaping).
2. python scripts/build.py build freeform \
--set title='My Page' \
--set subtitle='Optional subhead' \
--set [email protected] \
--out artifact.html
--set KEY=VALUE assigns a literal string; --set KEY=@FILE loads the file
contents verbatim into that spec field. Repeat for any field. Works for
body_html, extra_css, extra_js, eyebrow, page_class, and the same
*_html fields in any other template (summary_html, intro_html,
details_html, …).
Spec-file workflow (best for structured templates)
1. python scripts/build.py describe <template> # required keys + skeleton
2. write spec.json
3. python scripts/build.py build <template> --spec spec.json --out artifact.html
For templates with typed slots (pr_review.findings[], slide_deck.slides[],
status_report.metrics[]), the spec file is the right shape — the template
reasons over the structure. For freeform, the spec is mostly a thin config
wrapper around one HTML string; the --set flow above is usually less
friction.
What ships with it
23 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.
- .gitignore 19 B
- assets/base.css 9.0 KB
- assets/base.js 6.3 KB runs code
- CHANGELOG.md 4.4 KB
- README.md 5.1 KB
- references/palette.md 3.4 KB
- references/templates.md 13 KB
- scripts/build.py 9.3 KB runs code
- scripts/checker.py 13 KB runs code
- scripts/composer.py 10 KB runs code
- scripts/templates/__init__.py 1.1 KB runs code
- scripts/templates/deck.py 4.5 KB runs code
- scripts/templates/design.py 8.0 KB runs code
- scripts/templates/diagram.py 7.3 KB runs code
- scripts/templates/editor.py 12 KB runs code
- scripts/templates/exploration.py 8.8 KB runs code
- scripts/templates/freeform.py 1.6 KB runs code
- scripts/templates/prototype.py 6.1 KB runs code
- scripts/templates/report.py 6.8 KB runs code
- scripts/templates/research.py 4.6 KB runs code
- scripts/templates/review.py 9.6 KB runs code
- tests/test_checker.py 5.5 KB runs code
- tests/test_smoke.py 18 KB runs code
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 · 296 lines · 151 tokens per session scan A 8f895e2cddce
composing-html is a skill published in the GitHub repository oaustegard/claude-skills (154 stars, last pushed 2d ago), licensed MIT. It adds 151 tokens to every session and 3,339 once invoked, about $0.0006 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.
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