Effective HTML is a collection of agent skills for creating self-contained HTML artifacts such as wireframes, interactive prototypes, plans, diagrams, reports, and tools. It helps coding agents turn reference material and prompts into visual, usable HTML deliverables, and the catalogue entries are its installable skills and plugins.
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 plannotator/effective-html --skill htmlgit clone --depth 1 https://github.com/plannotator/effective-htmlWrote 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/plannotator/effective-html/html)<a href="https://agentmods.dev/skills/plannotator/effective-html/html"><img src="https://agentmods.dev/badge/skills/plannotator/effective-html/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/plannotator/effective-html/html"><img src="https://agentmods.dev/badge/skills/plannotator/effective-html/html.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector pass
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 | $0.00107 | $0.01303 |
| Opus 5.5 | $0.00043 | $0.00521 |
| Sonnet 5.5 | $0.00021 | $0.00261 |
| Haiku 4.5 | $0.00011 | $0.00130 |
Grade A, and why
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 — 78 lines — stays where its author put it; the contents beside it link to each section on GitHub.
HTML
Build one self-contained HTML file that makes the subject clearer, easier to use, or easier to understand. The standard is consistent care, not a consistent look. Do not reproduce a house palette, typography stack, card system, or layout from prior runs.
Route the request first
Use the narrowest skill that owns the main review question:
- Read and compose
design-artifactwith the chosen workflow when palette, type, composition, theming, or overall visual register remain open. It provides creative direction; it does not replace the specialist that owns fidelity, structure, or behavior. - Read and follow
html-wireframewhen structure, information hierarchy, navigation, or task flow is still unsettled. It should remain visibly low fidelity and may compare two or three layout directions. - Read and follow
html-prototypewhen the user needs a polished mockup or a working interactive flow. A mockup is the static fidelity mode inside that skill. - Read and follow
html-planwhen the artifact is primarily a plan, roadmap, implementation sequence, or rollout document whose source commitments must remain easy to verify. - Read and follow
html-diagramwhen relationships, sequence, topology, state, hierarchy, or system behavior are the main content. - Continue with
htmlfor reports, explainers, presentations, landing pages, data stories, tools, and mixed artifacts that do not have a clearer owner.
These sibling links are the nesting mechanism when the collection is installed together. If a specialized skill is unavailable, continue here and load the closest reference below. Do not make the user install another skill before completing the request.
Read the room before designing
Inspect the user's request and any material they supplied. When working in a repository, look for its design language in AGENTS.md, CLAUDE.md, design-system documentation, tokens, existing components, and nearby artifacts.
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 · 78 lines · 107 tokens per session scan A d99612ae158c
html is a skill published in the GitHub repository plannotator/effective-html (3,717 stars, last pushed 6d ago), licensed MIT. It adds 107 tokens to every session and 1,303 once invoked, about $0.0004 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.
Other skills, from other repositories
playground
Creates interactive HTML playgrounds — self-contained single-file explorers that let users configure something visually through controls, see a live preview, and copy out a prompt. Use when the user asks to make a playground, explorer, or interactive tool for a topic.
frontend-ui-engineering
Builds production-quality, accessible, responsive user-facing UIs. Use when building or modifying interfaces and pages, creating components, implementing layouts, meeting WCAG accessibility requirements, managing state, or when the output needs to look and feel production-quality rather than AI-generated.
frontend-design
Guidance for distinctive, intentional visual design when building new UI or reshaping an existing one. Helps with aesthetic direction, typography, and making choices that don't read as templated defaults.
web-design-engineer
Build or redesign polished browser-rendered visual artifacts with HTML/CSS/JavaScript/React: pages, dashboards, prototypes, slide decks, animations, UI mockups, and data visualizations. Use for visual front-end creation, design-system exploration, design critique, or explicit browser acceptance / QA of a web artifact.…
baseline-ui
Quickly deslop UI code by fixing spacing, hierarchy, typography, and small layout issues. Use when the interface needs a fast cleanup or polish pass.
migrate
Apply DESIGN, canon, and modules to every page in the inventory, producing a deployable static HTML site. Use to migrate or render the whole captured site into the redesigned static tree ("migrate the pages", "render the migrated site", "apply the design to all pages", "build the deployable site", "convert the…