ELS MCP server

An MCP (Model Context Protocol) server that lets LLM agents (e.g. chatbots like Claude) make meaningful use of the data provided by the Explore Local Statistics API.

TypeScript/Node, served over Streamable HTTP. See CLAUDE.md and docs/ for the design reasoning behind the tool set. A previous Python/FastMCP proof-of-concept lives earlier in this repo's git history if old behaviour ever needs cross-checking.

Note: It is not possible to add custom MCP servers to some LLM chatbots, like M365 Copilot.

Run the server locally

Requires Node.js 20+.

npm install
cp .env.example .env   # then edit ELS_API_BASE_URL if needed
npm run dev

This starts the server at http://localhost:8001/mcp.

Connect it to your LLM

The example below is specific to Claude Desktop, but should be similar for other MCP-capable clients.

Open the Settings dialog, then the Developer tab, then Edit config. This opens a JSON configuration file — add:

{
  // ...EXISTING CONFIG ABOVE...
  "mcpServers": {
    "els-mcp-server": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "http://localhost:8001/mcp"]
    }
  }
}

Save the file, make sure npm run dev is running, and restart Claude Desktop.

Start using it

Check that your chatbot is connected by asking:

Are you able to connect to els-mcp-server?

Once connected, if you ask questions that can be answered with data on Explore Local Statistics, your chatbot should automatically call this server to give you an answer, e.g.:

Which local authority in Wales has the highest employment rate?

Related MCP server: UK ONS MCP Server

Other commands

npm run build         # production build (tsc -> dist/)
npm run lint           # eslint
npm run format          # prettier --write
npm run format:check    # prettier --check

Deploy to Vercel

1. Fork this repo to your own GitHub account.

2. In Vercel, create a new project from that repo. Vercel auto-detects the Node function in api/.

3. Set the ELS_API_BASE_URL environment variable in the Vercel project settings (see .env.example) — the app fails to start without it.

4. Deploy.

Use it with your LLM

Once deployed, add the MCP server to your favourite LLM chatbot. For Claude (web or desktop):

1. Go to Settings (Customize) → Connectors

2. Click +, then Add custom connector

3. Paste in the URL: https://<your-app>.vercel.app/mcp

4. Click Add, then Connect