What is html-playground?

A single-file HTML tool with controls, a live preview, and a prompt that users can copy. HTML is the language used to structure web pages.

Use it to build playgrounds, explorers, maps, critiques, diff reviews, and code maps with editable controls and visible results.

It makes interactive ideas easier to test in a desktop browser without setting up a larger application or external runtime.

html-playground — Skill for Claude Code and Codex by PaulRBerg

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.

Any agent

npx skills add PaulRBerg/agent-skills --skill html-playground

Clone the repo

git clone --depth 1 https://github.com/PaulRBerg/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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/paulrberg/agent-skills/html-playground/github.svg)](https://agentmods.dev/skills/paulrberg/agent-skills/html-playground)

Your own site

<a href="https://agentmods.dev/skills/paulrberg/agent-skills/html-playground"><img src="https://agentmods.dev/badge/skills/paulrberg/agent-skills/html-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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/paulrberg/agent-skills/html-playground"><img src="https://agentmods.dev/badge/skills/paulrberg/agent-skills/html-playground.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 46 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,074 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

Origin original 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.

Model	Per session	Once invoked
Fable 5.1	$0.00046	$0.01074
Opus 5.5	$0.00018	$0.00430
Sonnet 5.5	$0.00009	$0.00215
Haiku 4.5	$0.00005	$0.00107

Measured 17d ago against content hash 1c234cd5ad2c, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

html-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 17d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/prepare-debrief.sh), 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/html-playground/SKILL.md · 94 lines

How it starts

The opening of the file, as written. The whole thing — 94 lines — stays where its author put it; the contents beside it link to each section on GitHub.

HTML Playground Builder

Build a self-contained interactive HTML explorer with controls, live preview, and a copyable natural-language prompt.

Use debrief mode when the user asks for a debrief or a saved HTML findings/report from the current task, or invokes debrief [<slug>]. Otherwise, build a general playground.

Workflow

Infer the audience, decisions, and required states. Explicit requirements override the defaults below. Existing design systems override them, except the layout and theme defaults.
Read exactly one closest template and adapt it:
- templates/design-playground.md
- templates/data-explorer.md
- templates/concept-map.md
- templates/document-critique.md
- templates/diff-review.md
- templates/code-map.md
Write one HTML file with inline CSS and JavaScript and no external runtime dependencies.
Open it in a desktop browser, interact with every control and preset, and verify live preview, prompt output, copy feedback, empty/error states, and keyboard usability. Fix rendered defects before completion.

Debrief Mode

Persist current-task evidence as an interactive HTML report at ./.ai/debriefs/<slug>/index.html.

Derive a short topical kebab-case slug when omitted.
Write only inside the selected debrief directory. If an inferred slug already exists, choose a collision-free semantic qualifier, falling back to a timestamp suffix, and continue without overwriting. If the user explicitly supplied the slug, stop and ask whether to overwrite or choose a new slug.
Use only evidence present in the current task: real findings, paths, verified locations, metrics, decisions, and unresolved risks. Do not invent filler.

Before step 1, run the bundled preparer from the target repository:

bash <skill-dir>/scripts/prepare-debrief.sh <slug>

Use its DEBRIEFS_DIR, DEBRIEF_PATH, and EXISTS output. When EXISTS is true for an inferred slug, derive a unique slug and rerun the preparer before writing. When it is true for an explicit slug, request the choice defined above. Relay slug-validation errors and stop.

Read the full file on GitHub · 94 lines

Files

What ships with it

8 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.

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.

17d ago Changed · +6 lines 1c234cd5ad2c
1mo ago Changed · +37 lines · +16 tokens per session 8d6d5daf1f3f
2mo ago First seen · 51 lines · 30 tokens per session scan A dca22befb7f5

Subscribe to this mod's changes

html-playground is a skill published in the GitHub repository PaulRBerg/agent-skills (104 stars, last pushed 2d ago), licensed MIT. It adds 46 tokens to every session and 1,074 once invoked, about $0.0002 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.

CSS and styling Creative and media Frontend agent-skills ai-agents

html-playground next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
html-playgroundPaulRBerg/agent-skills	Skill	104	2d ago	MIT	A	46	Claude Code, Codex
anti-slop-designsickn33/agentic-awesome-skills	Skill	49k	2d ago	MIT	A	34	Claude Code
chakra-ui-builderchakra-ui/chakra-ui	Skill	41k	yesterday	MIT	A	214	Claude Code, Codex
visual-ralphYeachan-Heo/oh-my-codex	Skill	34k	today	MIT	A	52	Codex
open-design-setupcompozy/compozy	Skill	2.9k	today	MIT	A	67	Claude Code, Codex
edit-sitemicrosoft/power-platform-skills	Skill	1.1k	yesterday	MIT	A	104	Claude Code
prototype-webnexu-io/html-anything	Skill	9.5k	today	Apache-2.0	A	24	Claude Code, Codex