rocket: Skill for Claude Code

.agents/skills/modern-web-guidance/SKILL.md

modern-web-guidance is a skill for Claude Code, Codex from modernweb-dev/rocket. It costs 233 tokens per session (1,291 once invoked), scanned A, a copy of modern-web-guidance, MIT.

A reference search tool for current web-development practices covering HTML, CSS, and browser-side JavaScript. It provides guidance for common interface and performance tasks.

In plain words
What is it for?
Use it before building web interfaces, components, dialogs, popovers, layouts, or client-side behavior. It helps find relevant guidance for a specific web task.
Why use it?
Web standards and browser APIs change, so older examples can lead to outdated or inefficient implementations. This helps developers check recommended approaches before coding.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions CLAUDE.md; installed under .agents/ (shared by several agents); mentions AGENTS.md.

This is modernweb-dev/rocket's own configuration. It tells Claude Code and Codex how to work on rocket itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything rocket configures →

Reuse

Borrowing it

Nothing to install: this file belongs to modernweb-dev/rocket. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/modernweb-dev/rocket/main/.agents/skills/modern-web-guidance/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/modernweb-dev/rocket

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.

agentmods badge for modern-web-guidance

README.md
[![agentmods](https://agentmods.dev/badge/skills/modernweb-dev/rocket/modern-web-guidance/github.svg)](https://agentmods.dev/skills/modernweb-dev/rocket/modern-web-guidance)
Your own site
<a href="https://agentmods.dev/skills/modernweb-dev/rocket/modern-web-guidance"><img src="https://agentmods.dev/badge/skills/modernweb-dev/rocket/modern-web-guidance/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 modern-web-guidance

Your own site · 80×15
<a href="https://agentmods.dev/skills/modernweb-dev/rocket/modern-web-guidance"><img src="https://agentmods.dev/badge/skills/modernweb-dev/rocket/modern-web-guidance.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 233 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,291 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.
Origin 100% copy Near-identical to another mod 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 $0.00233 $0.01291
Opus 5.5 $0.00093 $0.00516
Sonnet 5.5 $0.00047 $0.00258
Haiku 4.5 $0.00023 $0.00129

Measured 2mo ago against content hash a1ed8448959e, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

modern-web-guidance 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.

Origin

This is a copy

100% identical to modern-web-guidance — 116 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/modern-web-guidance/SKILL.md · 115 lines

How it starts

The opening of the file, as written. The whole thing — 115 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Modern Web Guidance

A skill to search for specific web development use cases and retrieve their corresponding best practice guides.

When to use

Must use this skill:

  • At the start of implementing any web feature.
  • Before creating a new component, to check if a standardized pattern already exists.
  • To avoid implementing ad-hoc solutions or loading large dependencies unnecessarily.

Usage Instructions

Step 1. Search Use Cases

Search with an action-oriented query summarizing what you want to achieve using the search command. Run modern-web-guidance directly with npx.

npx -y modern-web-guidance@latest search "<query>" --skill-version 2026_05_16-c5e7870

Example Output:

[
  {
    "id": "optimize-image-priority",
    "description": "Optimize the loading priority of Largest Contentful Paint (LCP) candidate images.",
    "category": "performance",
    "featuresUsed": [ "Fetch priority" ],
    "tokenCount": 985,
    "similarity": 0.7289
  },
  {
    "id": "defer-rendering-heavy-content",
    "description": "Reduce rendering times in content-heavy web pages by deferring rendering for offscreen content.",
    "category": "performance",
    "featuresUsed": [ "content-visibility", "hidden=\"until-found\"" ],
    "tokenCount": 1250,
    "similarity": 0.6961
  }
]

Note: If search results are vague, return no matches, or show low similarity scores, run the list command to browse all guides:

npx -y modern-web-guidance@latest list

Step 2. Retrieve Best Practices

Once you have a relevant id from the search results, call this script using the retrieve command to get the full guide. You can pass multiple IDs separated by commas.

npx -y modern-web-guidance@latest retrieve "<id>"

Example Output: The markdown content of the guide describing implementation steps...

Using npx

  • IMPORTANT: on Windows, using npx may fail. Use npx.cmd ... instead.
  • Network access is required for fetching npm packages needed by the task.
  • If the npx -y modern-web-guidance… command hangs, you may be offline. Try running again in offline mode: npx --offline ….
  • The --skill-version flag is used to determine if this SKILL.md is out of date. If it is, a warning message is logged to stderr.

Read the full file on GitHub · 115 lines

Files

What ships with it

60 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 · 115 lines · 233 tokens per session scan A a1ed8448959e

Subscribe to this mod's changes

modern-web-guidance is a skill published in the GitHub repository modernweb-dev/rocket (395 stars, last pushed 8d ago), licensed MIT. It adds 233 tokens to every session and 1,291 once invoked, about $0.0009 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to modern-web-guidance, differing in 116 lines, and is treated as a copy.

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