Banner: Steam header for Eco by Strange Loop Games. Attribution use, not my artwork.

eco-mcp-app

An inline Claude Desktop widget for any public Eco game server [1]. Point at the "Eco via Sirens" [2] server (default) or any other Eco server by IP/hostname. Ask Claude "what's the Eco server doing?" and you get a live card: meteor countdown, online/total, world size, laws, economy, Discord CTA, Steam link.

Also a tech demo - a minimal, hand-rolled MCP Apps implementation [3] without a bundler or React. Whole iframe is one 300-line HTML file. Useful as a reference for building an MCP App in Python rather than the TypeScript/ext-apps [4] stack.

Live at eco-mcp.coilysiren.me/preview.

How it works

src/eco_mcp_app/server.py exposes tools that hit Eco's public /info endpoint and admin exporters, redact player names, and return content blocks: markdown fallback for text-only hosts + JSON for the iframe. The tool's _meta.ui.resourceUri points at ui://eco/status.html, registered as an MCP resource.

The iframe (src/eco_mcp_app/ui/eco.html) is plain HTML/CSS/JS - no build step. Hand-rolls the MCP Apps handshake per spec [5]:

1. Iframe → host: ui/initialize (with protocolVersion: 2026-01-26)

2. Host → iframe: initialize result

3. Iframe → host: ui/notifications/initialized

4. Host → iframe: ui/notifications/tool-result whenever a matching tool fires

The handshake is ~30 lines. The ext-apps SDK [4] does more, but for a read-only dashboard we don't need it.

Related MCP server: MCP Quickstart Weather Server

Tools

See docs/FEATURES.md for the full inventory. Headliner: get_eco_server_status. Plus tools for economy, world map, milestones, species, items, crafting, fair-price, ecoregions, government, climate. All accept an optional server arg (host, host:port, full URL).

Quick start

uv sync --group dev
coily smoke      # stdio test of all tools
coily http       # HTTP transport on :4000
coily harness    # browser dev harness on :8765

Add to Claude Desktop:

coily install-desktop

Deploy

Cloned from coilysiren/backend template. Dockerfile + deploy/main.yml (k3s) + .github/workflows/build-and-publish.yml. Target: https://eco-mcp.coilysiren.me/mcp/.

License & credits

MIT. Eco is a trademark of Strange Loop Games [1]; unofficial fan tool, not affiliated.

References

1. https://play.eco/

2. https://eco.coilysiren.me/

3. https://github.com/modelcontextprotocol/ext-apps

4. https://github.com/modelcontextprotocol/ext-apps/tree/main/sdk

5. https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx

See also

• AGENTS.md - agent-facing operating rules.

• docs/FEATURES.md - inventory of what ships today.

• .coily/coily.yaml - allowlisted commands.

Cross-reference convention from coilysiren/agentic-os#59.