scratch4js: Skill for Claude Code

.agents/skills/rslib-best-practices/SKILL.md

rslib-best-practices is a skill for Claude Code, Codex from playforge-coding/scratch4js. It costs 47 tokens per session (632 once invoked), scanned A, a copy of rslib-best-practices, MPL-2.0.

A set of guidelines for building Rslib projects, where Rslib is a tool for packaging JavaScript and TypeScript libraries. It covers configuration, commands, output files, dependencies, and integration with related build tools.

In plain words
What is it for?
Use it when creating, reviewing, or fixing Rslib configuration, builds, declaration files, package exports, or toolchain settings.
Why use it?
It provides project-specific choices for building libraries and checking their generated files. This reduces guesswork when configuring or troubleshooting an Rslib project.

Skill for Claude CodeCodex

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

This is playforge-coding/scratch4js's own configuration. It tells Claude Code and Codex how to work on scratch4js 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 scratch4js configures →

Reuse

Borrowing it

Nothing to install: this file belongs to playforge-coding/scratch4js. 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/playforge-coding/scratch4js/main/.agents/skills/rslib-best-practices/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/playforge-coding/scratch4js

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 rslib-best-practices

README.md
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Your own site
<a href="https://agentmods.dev/skills/playforge-coding/scratch4js/rslib-best-practices"><img src="https://agentmods.dev/badge/skills/playforge-coding/scratch4js/rslib-best-practices/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 rslib-best-practices

Your own site · 80×15
<a href="https://agentmods.dev/skills/playforge-coding/scratch4js/rslib-best-practices"><img src="https://agentmods.dev/badge/skills/playforge-coding/scratch4js/rslib-best-practices.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 47 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 632 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 $0.00047 $0.00632
Opus 5.5 $0.00019 $0.00253
Sonnet 5.5 $0.00009 $0.00126
Haiku 4.5 $0.00005 $0.00063

Measured 2mo ago against content hash f4444a526da6, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

rslib-best-practices 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 rslib-best-practices — 4 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/rslib-best-practices/SKILL.md · 59 lines

How it starts

The opening of the file, as written. The whole thing — 59 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Rslib Best Practices

Apply these rules when writing or reviewing Rslib library projects.

Configuration

  • Use rslib.config.ts and defineConfig
  • Check Rslib-specific configurations first (e.g., lib.*), and also leverage Rsbuild configurations (e.g., source.*, output.*, tools.*) as needed
  • For deep-level or advanced configuration needs, use tools.rspack or tools.bundlerChain to access Rspack's native configurations
  • In TypeScript projects, prefer tsconfig.json path aliases

CLI

  • Use rslib to build
  • Use rslib --watch to build in watch mode for local development
  • Use rslib inspect to inspect final Rslib/Rsbuild/Rspack configs

Output

  • Prefer to build pure-ESM package with "type": "module" in package.json
  • Prefer to use bundleless mode with output.target set to 'web' when building component libraries
  • Prefer to use bundle mode when building Node.js utility libraries
  • Ensure exports field in package.json is correctly configured and matches the actual JavaScript output and declaration files output of different formats (ESM, CJS, etc.)

Declaration files

  • Prefer to enable declaration file generation with lib.dts: true or detailed configurations
  • For faster type generation, enable lib.dts.tsgo experimental feature with @typescript/native-preview installed

Dependencies

  • Prefer to place dependencies to be bundled in devDependencies in bundle mode and dependencies in dependencies and peerDependencies will be automatically externalized (not bundled) by default
  • Verify the build output and dependency specifiers in package.json carefully to ensure no missing dependency errors occur when consumers install and use this package

Build optimization

  • Keep syntax target in lib.syntax aligned with real compatibility requirements to enable better optimizations
  • Avoid format-specific APIs in source code for better compatibility with different output formats
  • Prefer lightweight dependencies to reduce bundle size

Read the full file on GitHub · 59 lines

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 · 59 lines · 47 tokens per session scan A f4444a526da6

Subscribe to this mod's changes

rslib-best-practices is a skill published in the GitHub repository playforge-coding/scratch4js (2 stars, last pushed 4mo ago), licensed MPL-2.0. It adds 47 tokens to every session and 632 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to rslib-best-practices, differing in 4 lines, and is treated as a copy.

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