Registrum

UK Companies House MCP Server: due diligence and KYB (Registrum)

UK company due diligence and KYB: trace ownership to the beneficial owners, pull director histories, check ECCTA identity-verification status and deadlines, read parsed accounts. Live Companies House data, hosted, no key.

No Companies House developer account, no rate-limit handling, no iXBRL parsing. Works in Claude Desktop, Claude Code, Cursor, VS Code, and any MCP-compatible client. It also answers ChatGPT search and fetch.

Dependabot alerts and update pull requests are enabled on all six Registrum repositories; SECURITY.md says where to see the live alert count.

Try it now — no signup, no key, no install

Point your client at the hosted endpoint and every tool answers with real data:

https://registrum.co.uk/api/mcp

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

That is the whole setup. Ask it "Who ultimately owns BrewDog?" and it will trace the ownership chain to the named individuals who hold control.

One thing worth knowing before you test it on a household name: companies listed on a regulated market — Tesco, Rolls-Royce, most of the FTSE — are exempt from the PSC regime, so their ownership chain is legitimately empty and get_psc_chain says so rather than inventing a tree. Ownership questions are interesting on private companies, which is where the register actually records who is behind them.

The hosted endpoint has small daily caps, enough to see exactly what comes back. When you reach one, the tool tells you so and points at a free key; nothing silently degrades.

Three ways to use it

1. Try it - no key. Point your MCP client at https://registrum.co.uk/api/mcp and ask about any UK company. No signup.
2. Build with it - free key. 60 days of full access: every endpoint, no monthly cap, no card. After that the key stays free for light use.
3. Run on it - paid plan. When you need volume, premium endpoints or an SLA. Live prices and limits: GET /v1/plans.

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Why this instead of the Companies House API directly

Companies House publishes the raw register for free, and you can absolutely call it yourself. What you then own is the plumbing:

Doing it yourself	With Registrum
Register for a CH developer key, manage OAuth	Nothing, or one REGISTRUM_API_KEY
600 requests/5min, and you handle the 429s	Server-side throttling on a higher negotiated budget
Accounts arrive as iXBRL documents you must parse	get_financials returns turnover, net assets, profit/loss as numbers
PSC control types are raw codes	Decoded to plain English
Ownership chains: recurse yourself, handle cycles	get_psc_chain returns the resolved tree with termination reasons
Director networks: N+1 queries across appointments	get_network traverses to depth 2
Retry, cache, and survive CH outages yourself	24h/7d caching, circuit breaker, stale-while-revalidate

Other Companies House MCP servers make you bring your own CH key and hand back the raw response. This one does the enrichment.

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Running it with your own key

Use a key to build on it (60 days of full access), or when you would rather run the server locally than call ours.

Claude Desktop — ~/.claude/claude_desktop_config.json Cursor — .cursor/mcp.json (per project) or ~/.cursor/mcp.json (global)

{
  "mcpServers": {
    "registrum": {
      "command": "npx",
      "args": ["-y", "@registrum/mcp"],
      "env": { "REGISTRUM_API_KEY": "reg_live_..." }
    }
  }
}

Get a free key — 60 days of full access, no card.

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Tools

Tool	What you get
search_company	Find a company by name → company number
get_bundle	Profile, compliance, financials, PSCs and directors in one call - start here
get_company	Profile: status, age, SIC descriptions, overdue flags
get_financials	Turnover, net assets, profit/loss, employees — parsed from iXBRL, in GBP
get_directors	Current board with appointment history across all their companies
get_psc	Persons with Significant Control, control types in plain English
get_psc_chain	Ownership traversed to ultimate beneficial owners, with termination reasons
get_compliance	ECCTA identity-verification status — who has verified, who is pending, who is overdue
get_network	Companies connected by shared directors, to depth 2
search	For ChatGPT connectors and deep research: returns {results: [{id, title, url}]} for a company name
fetch	For ChatGPT connectors and deep research: takes a company:<number> id from search, returns the profile as a citable document

Resources

The same data is also exposed as MCP resource templates, for clients that attach context by URI. Each returns the JSON of the matching tool, goes through the same usage limits, and accepts a short numeric number (it is zero-padded to 8 characters).

Resource	Same JSON as
company://{number}/profile	get_company
company://{number}/financials	get_financials
company://{number}/psc	get_psc
company://{number}/compliance	get_compliance

On get_bundle

Most questions about a company need several of these views at once. get_bundle returns them in a single request: one call and one credit instead of five, and one round trip instead of five. Pass include to fetch a subset, or omit it for all five sections.

Each section carries exactly what its own endpoint returns, because the bundle is composed from those same handlers rather than reimplemented - so plan gates, caching and the ECCTA rules behave identically either way.

A null section is not an error. Financials come back null for a company that has filed no machine-readable accounts, and compliance requires a Pro plan. Only a missing company is an error, and that is a 404. Report a null section as "not available", never as an absence of the underlying fact.

On get_compliance

The Economic Crime and Corporate Transparency Act requires every UK director and PSC to verify their identity with Companies House. Deadlines are per company, not one date: each existing director is due by their company's next confirmation-statement due date, so the date differs from company to company. Unverified officers can block filings once it passes.

The tool returns verified / pending / overdue counts plus each unverified person and their individual deadline. It deliberately distinguishes pending (deadline not yet reached — not a failure) from overdue (missed). Treating those as the same thing is the single easiest way to report a compliant company as non-compliant.

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Example prompts

"Is Tesco PLC compliant with ECCTA director verification, and who still needs to verify?"

"Pull the last filed financials for 00445790 and tell me if turnover grew."

"Who ultimately owns BrewDog? Trace the ownership chain to the individuals."

"Which companies share directors with Barratt Developments?"

"Search for 'Monzo' and show me status, incorporation date and directors."

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Plans

The anonymous endpoint needs no account at all. A free key gives 60 days of full access, then stays free for light use; paid tiers add volume, premium endpoints such as PSC chain traversal and the ECCTA compliance endpoint, and an SLA.

Prices and quotas are served live from GET /v1/plans — that endpoint is the source of truth, so this README does not duplicate the numbers and cannot go stale against them. Human-readable version at registrum.co.uk.

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Notes

• Company numbers are zero-padded 8-character strings: 00445790, SC000268.
• Responses are JSON, cached server-side (24h profiles/directors, 7d financials).
• The hosted endpoint is stateless and anonymous: it stores no account, and rate limiting is keyed on a hash of the calling IP rather than anything about you.
• The npm package sends User-Agent: @registrum/mcp/<version> so we can see which features developers actually use. No telemetry runs on your machine.

API reference · Issues · [email protected]