eli5-codex

Explain anything to anyone — with the visual HTML experience inside Codex.

eli5-codex is a Codex adaptation of DreambigOu/ELI5, a Claude Code skill for making explanations fit the person listening.

The original ELI5 skill can explain a database index to a child, an API failure to a manager, or a React hook to an engineer by changing its vocabulary, analogies, tone, depth, and framing. It also asks the agent to produce an HTML artifact with large visuals and very little text.

That last step is where Codex needed an adapter: Codex can load the skill, but does not automatically turn the requested HTML artifact into an inline visual. This project keeps the ELI5 approach and adds the missing rendering path.

What this project changes for Codex

1. The original ELI5 skill is bundled in the Plugin

The repository includes skills/eli5-codex/SKILL.md, so the audience-aware explanation workflow travels with the installation instead of requiring a separate manual copy.

2. HTML artifacts are handed to an MCP renderer

The bundled Skill tells Codex to pass its generated HTML to the render_html MCP tool. The MCP server returns the sanitized HTML together with an MCP Apps UI resource.

3. The result is rendered in a sandboxed UI

The UI resource renders the explanation in a nested sandboxed iframe. Scripts, forms, event handlers, external navigation, and unsupported external resources are removed or blocked in safe mode.

4. There is still a fallback

If a host does not mount MCP Apps UI, the tool returns a useful text and structured result instead of failing silently.

In short:

Original ELI5 Skill
  + Codex Plugin packaging
  + render_html MCP
  + MCP Apps UI resource
  = ELI5-style visual explanations in Codex

Usage

After installation, start a new Codex task and ask naturally, for example:

Explain DNS to me like I'm five.

or:

Explain API rate limiting to my manager.

When the request calls for the visual HTML artifact, eli5-codex uses render_html rather than returning raw HTML source.

Install

After this repository is pushed to GitHub:

codex plugin marketplace add Elonon901001/eli5-codex
codex plugin add eli5-codex@eli5-codex

In the ChatGPT desktop app, add the repository marketplace in the Plugins directory, install eli5-codex, and start a new Codex task.

Supported hosts

• ChatGPT desktop app — Codex
• Codex CLI

The Codex IDE extension does not currently support Plugins. Inline UI is host-controlled; the text fallback remains available.

Development

The Plugin lives under plugins/eli5-codex/:

plugins/eli5-codex/
├─ .codex-plugin/plugin.json   # Plugin manifest
├─ .mcp.json                   # Starts the bundled MCP server
├─ skills/eli5-codex/          # ELI5 Skill adapted for Codex
├─ server/                     # MCP server, sanitizer, and bundle
└─ ui/                         # MCP Apps UI source and bundle

Build and test the MCP server:

cd plugins/eli5-codex/server
npm ci
npm test
npm run bundle

Build and test the UI:

cd plugins/eli5-codex/ui
npm ci
npm run build
npm test

GitHub Actions runs these checks on every push and pull request.

Limitations

• JavaScript inside submitted HTML is disabled in the MVP.
• Whether the iframe appears inline depends on the Codex host's MCP Apps support.
• A local node runtime is required to start the bundled MCP server.

Attribution and license

The explanation workflow is adapted from DreambigOu/ELI5, licensed under MIT. The Codex MCP renderer and UI in this repository are also released under the MIT License; see LICENSE.