mdn-web-docs

mdn-web-docs is a skill for Claude Code, Codex from Neeeophytee/agent-stylebooks. It costs 64 tokens per session (670 once invoked), scanned A, original, MIT.

A writing guide for web-platform documentation based on MDN Web Docs. MDN is a reference and learning site for HTML, CSS, JavaScript, and browser features.

In plain words
What is it for?
Use it to draft, rewrite, or check references, tutorials, guides, learning material, compatibility notes, and examples for web developers.
Why use it?
It helps developers understand how a web feature works, including its syntax, exceptions, standards status, and browser behavior, without overstating compatibility.

Skill for Claude CodeCodex

Written for Claude Code and Codex: shipped in a Claude Code plugin, but also agents/openai.yaml present.

Part of the agent-stylebooks plugin — 16 skills shipped together

Good fit Use it to draft, rewrite, or check references, tutorials, guides, learning material, compatibility notes, and examples for web developers.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/neeeophytee/agent-stylebooks/mdn-web-docs
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 Neeeophytee/agent-stylebooks --skill mdn-web-docs
Clone the repo
git clone --depth 1 https://github.com/Neeeophytee/agent-stylebooks

Made for: Claude Code, Codex.

Or install agent-stylebooks, the plugin that ships this one along with the rest of its 16 skills.

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.

agentmods badge for mdn-web-docs

README.md
[![agentmods](https://agentmods.dev/badge/skills/neeeophytee/agent-stylebooks/mdn-web-docs/github.svg)](https://agentmods.dev/skills/neeeophytee/agent-stylebooks/mdn-web-docs)
Your own site
<a href="https://agentmods.dev/skills/neeeophytee/agent-stylebooks/mdn-web-docs"><img src="https://agentmods.dev/badge/skills/neeeophytee/agent-stylebooks/mdn-web-docs/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.

agentmods 80×15 button for mdn-web-docs

Your own site · 80×15
<a href="https://agentmods.dev/skills/neeeophytee/agent-stylebooks/mdn-web-docs"><img src="https://agentmods.dev/badge/skills/neeeophytee/agent-stylebooks/mdn-web-docs.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 64 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 670 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00064 $0.00670
Opus 5.5 $0.00026 $0.00268
Sonnet 5.5 $0.00013 $0.00134
Haiku 4.5 $0.00006 $0.00067

Measured 2mo ago against content hash 48ca71db44c5, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

mdn-web-docs 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 2mo 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.

skills/mdn-web-docs/SKILL.md · 71 lines

How it starts

The opening of the file, as written. The whole thing — 71 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MDN Web Docs

Explain the web platform clearly enough that readers can transfer the knowledge beyond a single copied example.

Preserve platform truth

  • Keep syntax, values, exceptions, standards status, browser behavior, and code exact.
  • Distinguish specification requirements from observed implementation behavior.
  • Do not infer compatibility. Request or link authoritative compatibility data.
  • Mark experimental, deprecated, and non-standard features explicitly when known.

Set the audience and page purpose

  1. Choose the reader level and list the knowledge the page assumes.
  2. Choose reference, guide, tutorial, or conceptual explanation as the primary purpose.
  3. State what the feature is and why a developer would use it before deep detail.
  4. Order reference information predictably; order learning content from a working mental model to a useful example and then edge cases.
  5. Link prerequisites instead of reteaching an entire foundational topic.

Explain clearly

  • Use clear, concise, consistent terminology.
  • Keep one main idea per sentence and use active voice when it clarifies the actor.
  • Define an unfamiliar term before relying on it.
  • Explain what code does and why the relevant line matters. Do not narrate every token.
  • Use examples to reveal behavior, parameters, and edge cases, not as decoration.
  • State assumptions about document structure, security context, network state, or browser support.
  • Prefer inclusive, literal language and avoid jokes that obscure technical meaning.

Build useful examples

  • Make the smallest example that still demonstrates realistic behavior.
  • Include all required setup or label omitted scaffolding clearly.
  • Use safe placeholder data and accessible markup.
  • Keep names consistent across HTML, CSS, JavaScript, and prose.
  • Explain the expected result and a common failure when it adds learning value.
  • Do not present a clever shortcut as the default if it harms readability or safety.

Format the page

  • Use sentence-case headings that describe the section's information.
  • Use backticks for elements, attributes, properties, methods, values, and code.
  • Put sequential instructions in numbered lists and independent criteria in bullets.
  • Use notes sparingly. Put facts required for correct use in the main text.
  • Link to the relevant specification or authoritative source when normative detail matters.

Read the full file on GitHub · 71 lines

Files

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.

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.

  1. 2mo ago First seen · 71 lines · 64 tokens per session scan A 48ca71db44c5

Subscribe to this mod's changes

mdn-web-docs is a skill published in the GitHub repository Neeeophytee/agent-stylebooks (78 stars, last pushed 2mo ago), licensed MIT. It adds 64 tokens to every session and 670 once invoked, about $0.0003 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.

Related

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