How to connect Claude to Companies House data with MCP

What you need

You need a free API key and a Claude account. Steps checked against Anthropic's documentation on 19 October 2026; if a menu label differs, look for the nearest equivalent.

1. Get a key with the button on the developer docs page, or with one request: curl -X POST https://data.globalmindsetmarketing.co.uk/v1/keys/free -H "Content-Type: application/json" -d '{}'. The key starts with ukcd_ and is shown once.
2. Decide where you use Claude: claude.ai in a browser, the Claude Desktop app, the mobile apps or Claude Code in a terminal.

The free key gives 50 requests a month. Each tool call Claude makes counts as one request, and a single question can trigger two or three calls, for example a name search followed by a company lookup.

claude.ai and Claude Desktop: add a custom connector

claude.ai and Claude Desktop share the same connector list, so you add the server once. Custom connectors are available on Free, Pro, Max, Team and Enterprise plans; a Free account can add one custom connector.

Free, Pro and Max

1. Open Customize, then Connectors (in older layouts: Settings, Connectors).
2. Click Add custom connector.
3. Name it, for example UK Company Data.
4. Paste the server URL with your key:

https://data.globalmindsetmarketing.co.uk/mcp?key=YOUR_KEY

1. For authentication choose No sign-in. Our server uses API keys, not OAuth.
2. Click Add. Claude lists the tools it found.

Some organisations see a Request headers section in the dialog. Anthropic describes it as a beta for a limited set of organisations. If you have it, you can use the plain URL without ?key= and add the header authorization with the value Bearer YOUR_KEY. Authentication settings cannot be edited later, so to switch methods, remove the connector and add it again.

Team and Enterprise

An Owner adds the connector first under Organization settings, Connectors, Add, Custom, using the same URL. Members then find it under Customize, Connectors, marked Custom, and click Connect. Because the key is in the URL, everyone who connects shares one key and one monthly quota. For a team, an API Pro key (5,000 requests a month) is the practical choice.

Mobile

Add the connector on the web or in Claude Desktop. It then appears in the iOS and Android apps after you sign in.

Claude Code: one command

Claude Code can send an Authorization header, so the key stays out of the URL:

claude mcp add --transport http uk-company-data https://data.globalmindsetmarketing.co.uk/mcp --header "Authorization: Bearer YOUR_KEY"

Add --scope user to make it available in all your projects. The default scope, local, applies to the current project only; --scope project writes the server to a shared .mcp.json file. In a shared file, reference an environment variable instead of pasting the key:

{
  "mcpServers": {
    "uk-company-data": {
      "type": "http",
      "url": "https://data.globalmindsetmarketing.co.uk/mcp",
      "headers": { "Authorization": "Bearer ${UKCD_KEY}" }
    }
  }
}

Run claude mcp list to check the connection, or type /mcp inside a session to see the server's status and tools.

Use it in a chat

In claude.ai, click + in the message box, open Connectors and make sure UK Company Data is switched on for the conversation. Then ask a question that names a company or a company number. The first time Claude calls a tool it asks for approval. You can set each tool to Always allow, Needs approval or Blocked from the connector's page under Customize, Connectors.

Example prompts:

• "Find TESCO PLC and tell me its company number, status and when its next accounts are due."
• "Is company 10623966 up to date with its filings? Show its last three balance sheets."
• "Compare 10623966 with 00445790 on net assets and cash."
• "Which companies published new accounts in the last 7 days?"
• "Add 10623966 to my watchlist, then show me any alerts."

Large groups that file only PDF accounts, such as TESCO PLC, return register details but no parsed figures.

Tools Claude can call

The watchlist is tied to your key, so it is the same list whether you use Claude, Claude Code or the REST API. Expect "no figures" for many young companies: on 1 October 2026, 1,341,352 active companies (26.0%) had not filed any accounts yet (accounts types data).

Keep the key safe

A key in a URL can end up in screenshots, browser history and shared settings. Treat the connector URL like a password, prefer the header method where your client supports it, and do not paste the key into a chat message. If a key leaks, create a new one, replace the connector and email info@globalmindsetmarketing.co.uk to have the old key revoked.

Troubleshooting

The server lists its tools without a key, so a connector can look healthy even when the key is missing. The first real tool call is the test. For setup in other clients, see the ChatGPT connector guide, the Cursor guide and the MCP server overview.

Sources

• Claude docs: add a connector that is not in the directory
• Claude Help Center: getting started with custom connectors
• Claude Code docs: connect to MCP servers

Sources: Companies House register and accounts data (Open Government Licence v3.0), legislation.gov.uk and GOV.UK guidance where linked. This page is general information, not legal, tax or credit advice. Spotted an error? Email info@globalmindsetmarketing.co.uk.