The site offers the h5p-author skill as zips to install in Claude and ChatGPT

vite.config.ts writes two zips into /h5p/skill/ from the pinned author package, the files
that folder serves: h5p-author.zip, the skill's folder at its root, which Claude's app takes,
and h5p-author-chatgpt.zip, the same files under skills/h5p-author/ with an Agent Plugins
plugin.json, which ChatGPT's Plugins take. Every entry has one date, so a pin writes the
same bytes each build. @zip.js/zip.js becomes a direct dependency, at the version the
lockfile already held.

The guide gets "Or install the skill once": Claude, ChatGPT, Open WebUI and agents with a
terminal. The skill page and the README point to it.

Closes #40.

Author: alekswebnet

README.md

@@ -9,7 +9,7 @@ The site of the [missing-elements](https://github.com/missing-elements) web comp
 | `/` | The project list, the tools (the build page, which links the skill's page), and a footer of links | [src/index.njk](src/index.njk); the lists are in [src/_data/site.js](src/_data/site.js) |
 | `/pdfjs-viewer/` | The docs of `<pdfjs-viewer-element>`, with a live preview | [src/pdfjs-viewer/](src/pdfjs-viewer/) |
 | `/h5p/build/` | The build page, for people: what it makes, a sample that plays, and the build of a chat's source into a `.h5p`, in the visitor's browser | [src/h5p/build/](src/h5p/build/) |
-| `/h5p/skill/` | The skill's files, and a page that lists each at its full address, for a chat | [src/h5p/skill/](src/h5p/skill/), copied by [eleventy.config.js](eleventy.config.js) |
+| `/h5p/skill/` | The skill's files, and a page that lists each at its full address, for a chat; and the skill as zips to install: `h5p-author.zip` for Claude, `h5p-author-chatgpt.zip` for ChatGPT's Plugins | [src/h5p/skill/](src/h5p/skill/), copied by [eleventy.config.js](eleventy.config.js); the zips written by [vite.config.ts](vite.config.ts) |
 | `/h5p/bundles/` | The skill's build tool and a library bundle per content type, for a chat that runs Node but cannot reach npm | written by [vite.config.ts](vite.config.ts) |
 | `/h5p/build/types/` | The skill's type files, which the build page copies for the chat | written by [vite.config.ts](vite.config.ts) |
 

package.json

@@ -32,6 +32,7 @@
     "@missing-elements/h5p-libraries": "1.1.0",
     "@missing-elements/h5p-offline-player": "1.6.0",
     "@missing-elements/h5p-runtime": "1.0.1",
-    "@missing-elements/pdfjs-viewer": "4.5.0"
+    "@missing-elements/pdfjs-viewer": "4.5.0",
+    "@zip.js/zip.js": "2.24.0"
   }
 }

pnpm-lock.yaml

@@ -12,6 +12,7 @@ socialImage:
   alt: "The build page: its headline, Build an H5P activity with AI, and a course presentation playing beside it."
 # The top bar's links to the page's own sections (topbar.njk).
 topbarLinks:
+  - { href: "#install", text: "Install" }
   - { href: "#prompts", text: "Prompts" }
   - { href: "#types", text: "Types" }
   - { href: "#open-source", text: "Open source" }
@@ -39,7 +40,8 @@ csp: "default-src 'self'; script-src 'self'; style-src 'self'; img-src 'self'; o
       H5P. It writes the activity, and <a href="/h5p/build/">the build page</a> makes it a
       <code>.h5p</code> file for Moodle or any other H5P site. Both are free and
       <a href="#open-source">open source</a>, with no account and nothing to install: you need only a
-      chat that can open a web page.
+      chat that can open a web page. In Claude or ChatGPT you can also
+      <a href="#install">install the skill once</a>.
     </p>
     <p><a class="button button-solid button-large" href="/h5p/build/">Open the build page</a></p>
   </header>
@@ -111,6 +113,40 @@ csp: "default-src 'self'; script-src 'self'; style-src 'self'; img-src 'self'; o
     </p>
   </section>
 
+  {#- The zips are written by vite.config.ts from the release the site pins, so each holds the skill
+      the prompt above sends a chat to. Each was uploaded as it is, by the owner, on 2026-11-13. -#}
+  <section aria-labelledby="install">
+    <h2 id="install">Or install the skill once</h2>
+    <p>
+      Installed, the skill stays in your chat: ask for an activity with no address to paste, such as
+      "Use the h5p-author skill to make a quiz of five questions on the rivers of Europe".
+    </p>
+    <ul>
+      <li>
+        <strong>Claude</strong>, on claude.ai or in its apps: download
+        <a href="/h5p/skill/h5p-author.zip" download>h5p-author.zip</a> and upload it under Customize,
+        then Skills, with code execution on. Claude builds the <code>.h5p</code> file in the chat.
+      </li>
+      <li>
+        <strong>ChatGPT</strong>: download
+        <a href="/h5p/skill/h5p-author-chatgpt.zip" download>h5p-author-chatgpt.zip</a> and upload it
+        under Plugins. ChatGPT cannot install the build tool, so it hands over a link to the build
+        page. If the page says the link arrived damaged, ask for the link again, or for the source
+        as a file, and open that on the build page.
+      </li>
+      <li>
+        <strong>Open WebUI</strong>: an administrator imports the skill under Import from URL, from
+        its folder on GitHub,
+        <code>https://github.com/missing-elements/h5p-offline-player/tree/main/skills/h5p-author</code>.
+      </li>
+      <li>
+        <strong>An agent with a terminal</strong>, such as Claude Code, Codex or Cursor:
+        <code>npx skills add missing-elements/h5p-offline-player --skill h5p-author</code>.
+      </li>
+    </ul>
+    <p>The zips hold h5p-author {{ skill.version }}, the release the build page runs.</p>
+  </section>
+
   <section aria-labelledby="prompts">
     <h2 id="prompts">Prompts to start from</h2>
     <p>

src/h5p/create-with-ai/index.njk

@@ -38,7 +38,9 @@ csp: "default-src 'self'; script-src 'self'; style-src 'self'; img-src 'self'; o
     </p>
     <p>
       Where skills can be installed, install it instead:
-      <code>npx skills add missing-elements/h5p-offline-player --skill h5p-author</code>.
+      <code>npx skills add missing-elements/h5p-offline-player --skill h5p-author</code>, or in
+      Claude's or ChatGPT's app from the zips at
+      <a href="{{ site.url }}/h5p/create-with-ai/#install">{{ site.url }}/h5p/create-with-ai/#install</a>.
     </p>
   </header>
 

src/h5p/skill/index.njk

@@ -3,6 +3,7 @@ import { copyFile, mkdir, readFile, rm, writeFile } from 'node:fs/promises'
 import { basename, join, resolve } from 'node:path'
 import { fileURLToPath } from 'node:url'
 import { buildPackage, writeBundles } from '@missing-elements/h5p-author'
+import { Uint8ArrayReader, Uint8ArrayWriter, ZipWriter } from '@zip.js/zip.js'
 import { build, defineConfig, type Plugin } from 'vite'
 
 /*
@@ -202,12 +203,99 @@ function bundles(): Plugin {
   }
 }
 
+/** One date for every entry, as `h5p-author bundle` writes its zips: the same pin writes the same bytes. */
+const ZIP_DATE = new Date(2000, 0, 1, 2)
+
+/**
+ * The h5p-author skill as zips to install, beside the files `/h5p/skill/` serves, from the same
+ * pinned author package:
+ *
+ * - `h5p-author.zip`: the skill's folder at the zip's root, `h5p-author/SKILL.md`, which Claude's
+ *   app takes under Customize, Skills (as does Open WebUI's import).
+ * - `h5p-author-chatgpt.zip`: the same files as a plugin, under `skills/h5p-author/`, with its
+ *   `plugin.json` at the root, which ChatGPT's Plugins take. A zip with the folder at its root is
+ *   refused there ("Plugin archive must contain … `skills/*\/SKILL.md`"). The manifest is the Agent
+ *   Plugins one, which allows no field but its own ten, with ChatGPT's name for the plugin under
+ *   `extensions`; a name that leads with "H5P" says who made it.
+ *
+ * Both were uploaded as they are written here, by the owner on 2026-11-13. ChatGPT's code cannot
+ * read a plugin's files, so neither carries the build tool: where a chat cannot install it, the
+ * build page builds.
+ */
+function skillZips(): Plugin {
+  const author = new URL('./node_modules/@missing-elements/h5p-author/', import.meta.url)
+  const guide = 'https://missing-elements.github.io/h5p/create-with-ai/'
+  let outDir = ''
+  return {
+    name: 'missing-elements:skill-zips',
+    apply: 'build',
+    configResolved(config) {
+      outDir = resolve(config.root, config.build.outDir)
+    },
+    async writeBundle() {
+      const { version } = JSON.parse(await readFile(new URL('package.json', author), 'utf8')) as { version: string }
+      // The files eleventy.config.js copies to /h5p/skill/: SKILL.md, the licence and references/.
+      const references = readdirSync(new URL('references/', author), { recursive: true, withFileTypes: true })
+        .filter((entry) => entry.isFile())
+        .map((entry) => join(entry.parentPath, entry.name).slice(fileURLToPath(author).length).split('\\').join('/'))
+      const files = ['SKILL.md', 'LICENSE', ...references].sort()
+      const skill = await Promise.all(files.map(async (path) => [path, await readFile(new URL(path, author))] as const))
+      const manifest = {
+        $schema: 'https://agent-plugins.org/schemas/1.0.0/plugin.schema.json',
+        name: 'h5p-author',
+        version,
+        description: 'Create H5P content from a prompt, a lesson or supplied material, as a playable .h5p: quizzes, flash cards, presentations, interactive books and more.',
+        author: { name: 'Missing Elements', url: 'https://github.com/missing-elements' },
+        homepage: guide,
+        repository: 'https://github.com/missing-elements/h5p-offline-player',
+        license: 'MIT',
+        keywords: ['h5p', 'quiz', 'e-learning', 'authoring'],
+        extensions: {
+          'com.openai': {
+            interface: {
+              displayName: 'H5P Author by Missing Elements',
+              shortDescription: 'Make a playable H5P activity from a prompt or your material',
+              developerName: 'Missing Elements',
+              websiteURL: guide
+            }
+          }
+        }
+      }
+      const folder = join(outDir, 'h5p', 'skill')
+      await mkdir(folder, { recursive: true })
+      await writeFile(join(folder, 'h5p-author.zip'), await zipOf('h5p-author/', skill))
+      await writeFile(join(folder, 'h5p-author-chatgpt.zip'), await zipOf('skills/h5p-author/', skill, [['plugin.json', new TextEncoder().encode(`${JSON.stringify(manifest, null, 2)}\n`)]]))
+    }
+  }
+}
+
+/**
+ * A zip of the files under `prefix`, after the files at its root, with an entry for each folder
+ * before what is in it, as `git archive` writes one: the shape of the zips first uploaded.
+ */
+async function zipOf(prefix: string, files: ReadonlyArray<readonly [string, Uint8Array]>, atRoot: ReadonlyArray<readonly [string, Uint8Array]> = []): Promise<Uint8Array> {
+  const writer = new ZipWriter(new Uint8ArrayWriter(), { useWebWorkers: false, lastModDate: ZIP_DATE, extendedTimestamp: false })
+  for (const [path, bytes] of atRoot) await writer.add(path, new Uint8ArrayReader(bytes))
+  const folders = new Set<string>()
+  for (const [path, bytes] of files) {
+    const parts = `${prefix}${path}`.split('/')
+    for (let depth = 1; depth < parts.length; depth++) {
+      const name = `${parts.slice(0, depth).join('/')}/`
+      if (folders.has(name)) continue
+      folders.add(name)
+      await writer.add(name, undefined, { directory: true })
+    }
+    await writer.add(`${prefix}${path}`, new Uint8ArrayReader(bytes))
+  }
+  return writer.close()
+}
+
 export default defineConfig({
   publicDir: false,
   // A missing file is a 404, as on GitHub Pages, not the home page: `pnpm preview` answers as the
   // site does, where an SPA's fallback would answer every address with a page.
   appType: 'mpa',
-  plugins: [emptyOwnFolders(), licenceFiles(), typeFiles(), sample(), bundles()],
+  plugins: [emptyOwnFolders(), licenceFiles(), typeFiles(), sample(), bundles(), skillZips()],
   build: {
     outDir: '_site',
     emptyOutDir: false,