Example: Arcade Server

An MCP Apps server that lets you browse and play classic arcade games from archive.org directly in an MCP-enabled host.

Legal Disclaimer

This is a technical demonstration, not a distribution platform.

Games are fetched directly from archive.org's embed system at runtime
We do not host, distribute, or store game content
Only games with verified distribution rights can be loaded
Games without verified rights are blocked

How Rights Verification Works

The server uses a strict verification system:

Curated Allowlist: Games in allowlist.ts have externally documented distribution rights with source URLs (publisher announcements, official websites). Each entry includes legal justification.
Metadata Verification: For games not in the allowlist, we check archive.org metadata for explicit rights indicators (shareware, freeware, public domain, Creative Commons).

Games are only allowed if they have verified rights. Unknown or restricted games are blocked.

What Games Are Available?

Shareware: First episodes/demos explicitly released for free distribution (DOOM, Duke Nukem, Commander Keen, Wolfenstein 3D, etc.)
Freeware: Games officially released as free by their publishers (Tyrian 2000, Jill of the Jungle)
Public Domain: Games with expired or waived copyright

See allowlist.ts for the complete list with legal documentation.

Emulator Runtimes

Archive.org uses the Emularity system to run games in the browser. This includes:

| Emulator | License | Used For | | ----------------------------------------------------- | ----------------------- | -------------------------------------------- | | DOSBox | GPL-2.0+ | DOS games | | EM-DOSBox | GPL-2.0+ | DOSBox compiled to JavaScript via Emscripten | | MAME | BSD-3-Clause / GPL-2.0+ | Arcade games |

Our relationship with these emulators:

We do not distribute, bundle, or modify any emulator code
Emulators are fetched directly from archive.org at runtime
We only proxy archive.org's embed system, which hosts its own copies of these emulators
The temporary in-memory caching (see below) is purely for CORS workaround purposes

License compatibility note:

The MCP Apps SDK is Apache-2.0 licensed. There is no license conflict because:

The arcade-server does not bundle, include, or link against GPL emulator code
Emulators are fetched from archive.org at runtime (like loading any CDN resource)
Emulators execute in the user's browser, a separate execution context
This is analogous to embedding a YouTube video - the embedding page isn't a derivative of YouTube's player

If you create a modified version that bundles emulator code into the distribution, you must comply with GPL-2.0+ terms (copyleft, source availability).

Script Re-hosting (CORS Workaround)

The server temporarily caches archive.org's emulation.min.js script in memory only (not persisted to disk) to work around browser security restrictions in sandboxed iframes. This is a technical necessity, not redistribution:

Cache uses Cache-Control: no-store headers
Cache is cleared on server restart
Script is fetched fresh from archive.org on first request
No modifications are made beyond replacing import() with loadScript() for iframe compatibility

Adding New Games

To add a game to the allowlist, you must provide:

sourceUrl: A link to an authoritative source documenting distribution rights (publisher website, press release, official announcement)
legalBasis: A clear explanation of why the game is legally distributable
Verification: Confirm the archive.org identifier works

When in doubt, do not add the game.

Overview

This example demonstrates serving external HTML content as an MCP App resource. The resource is a static loader that uses the MCP Apps protocol to receive tool arguments, then fetches the processed game HTML from a server endpoint. This pattern allows the same resource to display different games based on tool input.

Key techniques:

MCP Apps protocol handshake (ui/initialize → ui/notifications/tool-input) to receive game ID dynamically
Server-side HTML fetching and processing per game ID
<base href> tag for resolving relative URLs against archive.org
baseUriDomains CSP metadata to allow the base tag
Rewriting ES module import() to classic <script src> loading (for srcdoc iframe compatibility)
Local script endpoint to bypass CORS restrictions in sandboxed iframes
Rights checking to verify distribution permissions before loading games

Key Files

server.ts - MCP server with tool and resource registration
index.ts - HTTP transport and Express setup
game-processor.ts - Fetches and processes archive.org HTML
search.ts - Archive.org search with smart fallbacks and rights filtering
rights-checker.ts - Analyzes archive.org metadata for distribution rights
allowlist.ts - Curated list of verified shareware/freeware games
types.ts - Type definitions for rights management

Getting Started

npm install
npm run dev

The server starts on http://localhost:3002/mcp by default. Set the PORT environment variable to change it.

MCP Client Configuration

{
  "mcpServers": {
    "arcade": {
      "url": "http://localhost:3002/mcp"
    }
  }
}

Tools

| Tool | Description | UI | | ---------------- | -------------------------------------------- | --- | | search_games | Search for verified shareware/freeware games | No | | get_game_by_id | Load and play a verified-rights game | Yes |

search_games Parameters

| Parameter | Type | Default | Description | | ------------ | ------ | ------- | ------------------------ | | searchTerm | string | - | Game name or search term | | maxResults | number | 10 | Maximum results (1-50) |

get_game_by_id Parameters

| Parameter | Type | Default | Description | | --------- | ------ | ------- | ----------------------------------- | | gameId | string | - | Archive.org identifier for the game |

How It Works

1. Host calls search_games → Server searches allowlist + archive.org → Returns verified games only
2. Host calls get_game_by_id → Server verifies rights status
3. If rights verified → Tool returns success
4. If rights NOT verified → Tool returns error, game blocked
5. Host reads resource → Gets static loader with MCP Apps protocol handler
6. View performs ui/initialize handshake with host
7. Host sends tool-input with gameId → View fetches /game-html/:gameId
8. Server fetches embed HTML from archive.org and processes it:
   - Removes archive.org's <base> tag
   - Injects <base href="https://archive.org/"> for URL resolution
   - Rewrites ES module import() to <script src> loading
   - Fetches emulation.min.js, patches it, serves from local endpoint
   - Injects layout CSS for full-viewport display
9. Game runs: emulator loads ROM, initializes MAME, game is playable

Why the Processing?

Archive.org's game embed pages use ES module import() for loading the emulation engine. In srcdoc iframes (used by MCP hosts), import() fails because the iframe has a null origin. The server works around this by:

Fetching emulation.min.js server-side and replacing import() with window.loadScript()
Serving the patched script from a local Express endpoint (/scripts/emulation.js)
Using <script src> which is not subject to CORS restrictions, unlike fetch() or import()

Available Games (18 Verified Titles)

All games have verified distribution rights. See allowlist.ts for legal documentation.

id Software Shareware

| Identifier | Title | Year | | ------------------------------- | -------------------------------- | ---- | | doom-play | DOOM | 1993 | | msdos_DOOM_1993 | DOOM (MS-DOS) | 1993 | | wolfenstein-3d | Wolfenstein 3D | 1992 | | w3d-box | Wolfenstein 3D v1.4 | 1993 | | commander_keen_volume_one_131 | Commander Keen: Marooned on Mars | 1990 | | heretic-dos | Heretic | 1994 |

Apogee / 3D Realms Shareware

| Identifier | Title | Year | | ----------------------------------------------- | --------------------------- | ---- | | duke-nukem2-sw | Duke Nukem II | 1993 | | 3dduke13SW-altcontrols | Duke Nukem 3D | 1996 | | Bs-aog-sw1 | Blake Stone: Aliens of Gold | 1993 | | rise-of-the-triad-the-hunt-begins-version-1.0 | Rise of the Triad | 1994 | | biomenace1-sw | Bio Menace | 1993 | | Crystal-cave-sw1 | Crystal Caves | 1991 | | monster-bash1-sw | Monster Bash | 1993 | | halloween_harry_shareware | Halloween Harry | 1993 |

Epic MegaGames Shareware / Freeware

| Identifier | Title | Year | | ------------------------- | ----------------------------- | ---- | | Epic-pinball-sw1 | Epic Pinball | 1993 | | radsw20 | Radix: Beyond the Void | 1995 | | msdos_Tyrian_2000_1999 | Tyrian 2000 (Freeware) | 1999 | | jill-of-the-jungle-0mhz | Jill of the Jungle (Freeware) | 1992 |

MCP Servers