# Discussion Capsule

Discussion Capsule is a read-only MCP App that turns a GitHub Discussion into a compact, interactive brief inside an MCP host.

It demonstrates the contextual-launch pattern proposed in [modelcontextprotocol/ext-apps#736](https://github.com/modelcontextprotocol/ext-apps/pull/736): ordinary tool arguments identify the discussion, the server returns grounded structured content, and the app renders the result without introducing a host-specific launch envelope.

## What it does

- Loads a public GitHub Discussion, comments, and reply counts from GitHub's official REST API.
- Surfaces participants, answer state, source-linked open questions, and a filterable thread map.
- Lets a user ask the host model for reply help, then review and select a draft for copying.
- Never publishes, edits, reacts to, or otherwise mutates GitHub state.

Public discussions work without credentials. Set `GITHUB_TOKEN` only when you need a higher API rate limit or access to a private repository. Never commit the token.

## Run it

Requires Node.js 22 or newer.

```bash
npm install
npm run build
npm start
```

The Streamable HTTP MCP endpoint is `http://localhost:3001/mcp`. It binds to `127.0.0.1` by default. Use `PORT` or `HOST` to change either value; set a comma-separated `ALLOWED_HOSTS` list when exposing a non-loopback host.

For a stdio client:

```json
{
  "mcpServers": {
    "discussion-capsule": {
      "command": "node",
      "args": [
        "/absolute/path/to/mcp-discussion-capsule/dist/main.js",
        "--stdio"
      ]
    }
  }
}
```

Then ask the host:

> Open https://github.com/modelcontextprotocol/ext-apps/discussions/606 as a discussion capsule.

## Verify it

```bash
npm test
npm run build
npm run smoke:live
```

The live smoke test defaults to ext-apps Discussion #606. Pass another public Discussion URL as its first argument.

## Trust model

Discussion bodies and comments are untrusted external input. The app renders them as text, not executable HTML. Extracted questions are deterministic source excerpts with links; they are not claimed to be model judgments. GitHub remains the canonical source.

## AI disclosure

The initial prototype was developed with OpenAI Codex. The implementation was validated with local tests and a live GitHub Discussion; AI output is not treated as proof of GitHub state.