No key, no account, no install

UK company data in your AI client

Registrum serves an MCP endpoint that anyone can point a client at. It answers with live Companies House data: search, officers, filing and verification state, parsed accounts, and ownership traced through corporate shareholders to the people who actually hold control.

The whole setup

Add this to your MCP client’s config and restart it.

{
  "mcpServers": {
    "registrum": {
      "url": "https://registrum.co.uk/api/mcp"
    }
  }
}

In Claude Code it is one line instead: claude mcp add --transport http registrum https://registrum.co.uk/api/mcp

There is no key to paste and nothing to install. The endpoint is the product; an API key is what you get when you outgrow the free tier, not what you need to start.

Then ask it something

“Who ultimately owns BrewDog?”
“Is Monzo Bank up to date on its Companies House filings?”
“What were Gymshark's last reported turnover and net assets?”
“Which other companies do Deliveroo's directors sit on?”

Try ownership on a private company. Companies listed on a regulated market, which is most of the names you already know, are exempt from the PSC regime. Their ownership chain is legitimately empty, and get_psc_chain says so rather than inventing a tree. The register only records who is behind private companies, which is where the question is interesting anyway.

What the free tier gives you

Anonymous callers share one upstream Companies House budget with paying ones, so the free tier is metered in upstream cost rather than request count. Per day, per caller:

Tool	Cap	What it answers
search_company	30 a day	find a company by name
get_company	10 a day	profile, status, registered office
get_directors	10 a day	the board, with appointment history
get_compliance	10 a day	filing and ECCTA verification state
get_psc	5 a day	persons with significant control
get_financials	2 a day	parsed from iXBRL, in GBP
get_psc_chain	2 a day	ownership traced to real people
get_network	2 a day	director network to depth 2

The expensive ones are capped tightly because they are expensive: get_psc_chain fans out to thirty or more upstream calls to answer one question. When you reach a cap the tool tells you so and points at a free key. Nothing silently degrades.

Why it works this way

74% of the API keys Registrum has ever issued never made a single call. People were not leaving over price or documentation, they were leaving at the signup form. So the form came out of the path and the hosted endpoint became the product.

A key still exists, and it raises these caps immediately with no card. It is the thing you reach for once you already know the data is worth it. Get one free, or read the REST quickstart if you would rather call the API directly.

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