UK ONS MCP Server

A Model Context Protocol (MCP) server for the UK Office for National Statistics (ONS) CMD API (https://api.beta.ons.gov.uk/v1). Query official UK government statistics — inflation, GDP, wellbeing, trade, deaths and more — straight from your MCP-compatible assistant. No API key required.

Features

• Direct ONS access — no authentication, no tokens
• Browse & search the full published dataset catalogue
• Dimension discovery — inspect a dataset's dimensions and valid option codes before querying
• Real observations — pull data points filtered by geography, time and any other dimension
• Latest-data shortcut that auto-fills sensible defaults
• TypeScript, native fetch, zero runtime deps beyond the MCP SDK and Zod
• Input validation and actionable, self-correcting error messages

Requirements

• Node.js >= 18.17 (uses the global fetch and AbortSignal.timeout)

Recommended agent workflow

The ONS observations endpoint requires a value for every dimension of a dataset, and allows exactly one wildcard *. The intended flow is:

1. search_datasets — find a dataset id by keyword (e.g. "inflation" -> cpih01).
2. get_dataset_dimensions — learn the required dimensions and see sample option codes.
3. get_observation — request data, giving each dimension a value and using * for the one you want to vary.

get_latest_data is a convenience wrapper: it auto-fills time="*" and geography="K02000001" (UK) and any single-option dimension. If a dataset needs more choices, it returns the available options so you can switch to get_observation.

Available Tools

| Tool | Purpose | |------|---------| | list_datasets | Paginated list of all datasets (limit 1-1000, offset). | | search_datasets | Keyword search over id/title/description/keywords. | | get_dataset | Full metadata for one dataset by id. | | get_dataset_dimensions | Dimensions of a dataset's latest version, with option counts and samples. Call before get_observation. | | get_dimension_options | Page through the full list of valid option codes for one dimension. | | get_observation | Retrieve observations. Every dimension needs a value; exactly one may be *. | | get_latest_data | Latest observations with auto-filled time="*" / geography=UK defaults. |

Resources

| URI | Description | |-----|-------------| | ons://popular_datasets | Curated, live-verified list of common dataset ids. | | ons://api_info | API base URL, auth model and the recommended workflow. |

Example

Query CPIH (UK inflation) as a UK-wide time series:

// 1) discover dimensions
get_dataset_dimensions { "dataset_id": "cpih01" }
// -> dimensions: aggregate (122 options, e.g. CP00 "Overall Index"), geography, time

// 2) fetch the Overall Index across all time periods for the UK
get_observation {
  "dataset_id": "cpih01",
  "dimensions": { "time": "*", "geography": "K02000001", "aggregate": "CP00" }
}

Omitting a required dimension returns a helpful error listing what is missing and sample codes to use, so an agent can retry without guessing.

Installation & configuration

Option A — npx (published package)

No install step; the client runs it on demand.

Claude Desktop (claude_desktop_config.json) or Claude Code (.mcp.json):

{
  "mcpServers": {
    "uk-ons": {
      "command": "npx",
      "args": ["-y", "uk_ons_mcp_server"]
    }
  }
}

Option B — local build (from source)

git clone https://github.com/dwain-barnes/uk-ons-mcp-server.git
cd uk-ons-mcp-server
npm install
npm run build

Then point your client at the built entry point (use an absolute path):

{
  "mcpServers": {
    "uk-ons": {
      "command": "node",
      "args": ["/absolute/path/to/uk_ons_mcp_server/dist/index.js"]
    }
  }
}

On Windows, use a full path such as C:\\Users\\you\\uk_ons_mcp_server\\dist\\index.js.

Claude Code can also add it from the CLI:

claude mcp add uk-ons -- node /absolute/path/to/uk_ons_mcp_server/dist/index.js

Development

npm install
npm run build     # compile TypeScript to dist/
npm start         # run the built server on stdio
npm run dev       # tsc --watch
npm run clean     # remove dist/
npm test          # build, then run the end-to-end smoke test against the live API

The smoke test (test/smoke.mjs) spawns the built server over stdio with the MCP SDK client and checks all seven tools plus a resource end-to-end.

Security notes

• Read-only. Every tool only performs GET requests against the public ONS API; nothing is written or mutated.
• No authentication or secrets. The ONS CMD API is open and keyless, so there are no tokens to store or leak.
• Input validation. Dataset ids, editions, versions and dimension names are validated against a strict character set ([A-Za-z0-9._-], max 100 chars) and every path/query value is URL-encoded before a request is made. Dimension values may additionally be the single wildcard *.
• Bounded responses. Observation results are capped (with a truncated flag and total count) to avoid overwhelming the model's context.

License

MIT — see LICENSE.

Disclaimer This project is unofficial and not endorsed by the UK Office for National Statistics. Data usage remains subject to ONS terms and the Open Government Licence.