/generate-package-skill

name: generate-package-skill
description: Generate or update an Agent Skill that teaches consumers one npm or local package the user maintains, including framework modules and wrappers. Tests each example against the installed version. Use when a maintainer asks for a package Skill, a SKILL.md for their library, or a Skill update after a release.
license: MIT
compatibility: "Requires an agent with filesystem and shell access. Network access is needed for remote sources."

Generate a package Skill

Write a short Skill that stops an Agent from misusing one package version. The reader knows the language, the framework, and the domain. Write only what it would get wrong.

Inputs

Take a package name, directory, or prepared source. Ask for the destination only when it is missing. In a monorepo, put the Skill in the published package directory. Write one Skill per installed package, unless a second package has distinct users. Skip an internal package, whose users are the repository's own packages, such as a shared engine or types package. Report why, and write nothing. `assets/` holds the Harness request. A direct run ignores it.

1. Research

1. Record the exact version the destination branch publishes: its `package.json` version and the npm dist-tag that carries it. If npm `latest` is an older major, test the branch's version. If the branch is ahead of its last release, read source at that release tag and report the unreleased changes. 2. Read the manifest, every exported entry point, and the public types. For many sibling integrations, read the shared runtime and the most used few, and report which you sampled. 3. For a framework module, read what setup registers: auto-imports, components, the config key and defaults, hooks, server routes. 4. If the package wraps, re-exports, or peers on another package, read the types or tagged source of the version the consumer gets, never a default branch. 5. Read the current official docs and examples, and release notes only for breaking changes and removed APIs. When docs cover several frameworks, read the consumer's framework pages first, then the core pages they link.

To update an existing Skill after a release, use `update-package-skill`. It tests only what the release changed.

2. Test the examples

Observed behaviour beats documentation.

1. Create a minimal consumer fixture outside the package source. Install the recorded version, or link the local build. Before packing, build the package and its native code (NAPI, WASM); `prepack` can need them. Pack with the repository's package manager: `npm pack` leaves pnpm `catalog:` versions. Give the fixture its own `pnpm-workspace.yaml`, so a parent workspace cannot satisfy its imports. Install only the package, documented peers, and check tools such as `typescript`. A resolution error is a finding. Install each peer at npm `latest`. If `latest` is outside the peer range, test both versions. 2. Use consumer defaults. The package repository's config and fixtures can turn them off. In Nuxt, keep test modules out of `modules/`; Nuxt registers every module there. One fixture page can exercise many examples. 3. Run each example you include. Compare output with the claim: HTML, return values, type errors, build logs, exit codes, report files. Each concrete claim in prose is an example too: a value, count, default, result shape, error text, exit code, or bundle effect. Run it, or report it read from source. Run each example with one failure input as well, such as an unreachable URL, a bad token, or a stalled request. Run each example under each global setting the Skill describes, such as a staging environment or a site-wide switch. For each claim that a setting or dependency is required, run once without it and record what fails. Test each mode the package declares: framework modes (SSR, SPA, streaming, dev, build), each condition in `exports`, the oldest runtime in `engines`, and each CLI binary with a config file and with flags. Report other modes untested. Wrap every run in `timeout 120`. Grep the package for agent and CI detection, such as `CLAUDECODE` or `CI`; unset each variable it reads with `env -u VAR`. Read dev warnings in the dev log, prerender results in build output, and runtime results from the production server. If a trap says nothing happens, run it and confirm the silence. To fetch from a server, run [scripts/serve-fixture.mjs](scripts/serve-fixture.mjs) in the fixture: `node SKILL_DIR/scripts/serve-fixture.mjs --fetch / -- node .output/server/index.mjs`. Quote `'{port}'` in a server argument, since some shells expand it. `--header 'User-Agent: Googlebot/2.1'` sends a header, `Host` included. For a binary, use `--fetch-raw PATH --out DIR`. `DIR/responses.json` lists each status, content type, and response headers. For an HTTP client package, start a fake target on port 0 inside the test, and assert on the requests it receives. Without `--fetch`, it holds the server until SIGTERM. Background it with your tool's option; `&` and `nohup` die with the shell call. Start servers from your own test script and record each process ID you start; stop only those. Never kill by port or with `pkill -f`: another Agent can own that process. In a browser, set a desktop user agent; a package can treat `HeadlessChrome` as a bot. 4. If documentation and behaviour disagree, write the behaviour and report the mismatch. 5. Keep an unrunnable example only when the types prove it; report it untested.

Do not fix the package or its docs in the Skill change.

3. Write

Include:

• Setup that differs from the framework default, such as a required config key.
• What the package does automatically, and how to turn it off.
• Traps: silent failures, plausible wrong calls, documentation mismatches, version limits.
• One small example per common task the types do not make obvious.
• Breaking changes an Agent trained on an older