Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add f-labs-io/agent-html-skills/plugin install html-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/f-labs-io/agent-html-skills/html-interactive-playground)<a href="https://agentmods.dev/skills/f-labs-io/agent-html-skills/html-interactive-playground"><img src="https://agentmods.dev/badge/skills/f-labs-io/agent-html-skills/html-interactive-playground/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/f-labs-io/agent-html-skills/html-interactive-playground"><img src="https://agentmods.dev/badge/skills/f-labs-io/agent-html-skills/html-interactive-playground.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 | $0.00114 | $0.02647 |
| Opus 5 | $0.00057 | $0.01324 |
| Sonnet 5 | $0.00023 | $0.00529 |
| Haiku 4.5 | $0.00011 | $0.00265 |
Grade A, and why
html-interactive-playground 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.
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 — 161 lines — stays where its author put it; the contents beside it link to each section on GitHub.
HTML Interactive Playground
Some values are easier to find by feel than by reasoning — animation timings, easing curves, color combinations, threshold values, layout dimensions. A playground turns the parameter space into a UI: sliders for continuous values, dropdowns for discrete ones, live preview, and a Submit button.
This is the two-way interaction pattern: the user explores in the browser, then submits what worked back to the agent to apply for real.
Pre-flight — run BEFORE writing the artifact
Invoke html-skills:html-skills-listen (Skill tool) first; it is idempotent. If it returns a URL, inject it verbatim as window.__CLAUDE_SUBMIT_URL__ in the HTML you are about to write, ?t= query string included (a local, single-session loopback handshake — not a credential). If it reported web/sandbox mode, leave that line out; submitToClaude then falls back to clipboard mode.
When to use this skill
- "Help me tune X" / "Find the right value for Y"
- "Try different settings for Z and let me pick"
- "I'm not sure what value should be / what feels right"
- "Build a playground for X"
- Any time the user is in "I'll know it when I see it" territory
Output requirements
Real-time updating preview as the user manipulates controls. One Submit button that calls submitToClaude with the tuned values — the receiving agent reads the standard envelope and applies them.
Critical: the playground must work without explanation. Sliders should be labeled, ranges should be sensible, defaults should be the user's current values (or reasonable starting points).
Core structure
- Title — what's being tuned, in plain language
- Preview area — the thing the parameters control, prominently shown
- Controls — sliders/dropdowns/toggles for each parameter
- Current values display — show the chosen values as code/data, updating live
- Submit button — one button only. Calls
submitToClaudewith the chosen values in the standard payload envelope. The receiving agent extracts whatever shape it needs (CSS variables, JSON, JS object) from the envelope when responding — no need for parallel "copy as CSS" / "copy as JSON" buttons on the page. - Reset — back to defaults
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.
- 5d ago Changed · -48 lines 44c6078cd578
- 9d ago First seen · 209 lines · 114 tokens per session scan A 0fc75b3f1e7e
html-interactive-playground is a skill published in the GitHub repository f-labs-io/agent-html-skills (55 stars, last pushed 6d ago), licensed MIT. It adds 114 tokens to every session and 2,647 once invoked, about $0.0006 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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