Validate EU VAT numbers in Claude Desktop, Cursor, and ChatGPT

Your AI assistant can now check if a VAT number is real, pull the registered company name, and look up VAT rates for every EU country — all without leaving the chat. We just released vatnode-mcp, the official Model Context Protocol (MCP) server for vatnode.

This post covers what MCP is in 30 seconds, how to install the vatnode server in Claude Desktop / Cursor / ChatGPT, and a few concrete examples of why this is useful for anyone doing EU B2B work.

What MCP is (in 30 seconds)

Model Context Protocol is an open standard from Anthropic for connecting AI assistants to external tools and data sources. An MCP server exposes a small set of tools — named functions with described inputs — and the AI model picks the right one based on what the user is asking.

Think of it as the "USB-C of AI integrations": write one MCP server and any compatible client (Claude Desktop, Cursor, ChatGPT's custom-connectors, Cline, Continue, and more) can use it. The user just edits a config file once — no per-app integration work.

The five tools

vatnode-mcp ships five tools, four of them fully offline and free:

• get_country_vat_rates — standard, reduced, super-reduced and parking rates for a single country, plus the VAT number format and regex. Covers 45 European jurisdictions.
• list_eu_vat_rates — all 27 EU member states (plus XI for Northern Ireland) at once.
• check_vat_format — offline syntactic check of a VAT number against the country regex. Does not call VIES; great for a quick sanity check before burning quota.
• list_supported_countries — which countries support full VIES validation vs rate-lookup-only.
• validate_vat_number — live VIES validation. Returns validity, registered company name, address, registration date, and (when a requester VAT is configured on your vatnode account) a VIES consultation number for audit proof. Requires a free vatnode API key.

Why four free tools? Because the data is bundled into the package via eu-vat-rates-data (also open source) — there's nothing to charge for. The paid tool is the one that calls real VIES infrastructure.

Install

One config file edit. Open claude_desktop_config.json (on macOS: ~/Library/Application Support/Claude/) and add:

{
  "mcpServers": {
    "vatnode": {
      "command": "npx",
      "args": ["-y", "vatnode-mcp"],
      "env": {
        "VATNODE_API_KEY": "vat_live_..."
      }
    }
  }
}

Restart Claude Desktop. That's it. The vatnode tools appear in the tool picker. For Cursor, paste the same JSON in Settings → MCP → Add new server. ChatGPT custom connectors and other MCP clients (Continue, Cline) follow the same pattern.

The VATNODE_API_KEY is optional — without it you still get all four free tools. To enable live VIES validation, grab a free API key (no credit card; the free tier includes a monthly request quota).

What it actually looks like

A few real example exchanges (you don't have to name the tool — Claude picks it from the description):

The point isn't that Claude does VAT lookup faster than a Google search. It's that the result lands in the same conversation where you're drafting an invoice, double-checking a supplier, or writing checkout code — no context switch.

When this is genuinely useful

• Drafting invoices in chat:"Generate an invoice for this German customer — VAT ID DE123456789, rate to apply, reverse-charge note." Claude validates, looks up the rate, structures the document.
• Supplier due diligence: Paste a VAT number, get the registered company name and address. No tab switches to VIES.
• Writing tax-aware code:"Add VAT calculation for these countries to my checkout" — Claude pulls real rates and writes them into your code, not guesses from training data.
• Cross-border B2B onboarding: Drop a list of customer VATs, ask Claude to flag the invalid ones and pull company names for the rest.
• Auditing existing invoices:"Is the VAT on this 2024 invoice still valid?" — Claude re-checks now, you decide whether to chase the customer for an update.

Why use the official server

Third-party MCP marketplaces sometimes ship VAT-validation wrappers built around our public API. Using vatnode-mcp directly is the only way to:

• Keep your API key on your own machine — it never touches a hosted middle-tier
• Get tool descriptions that track the real API release-by-release (we're the ones shipping both)
• Skip an extra subscription tier on top of your vatnode plan
• Read the source — it's open and every release is signed with npm provenance — a cryptographic proof that the npm package was built from a specific commit in our public GitHub repo

What's next

The current release ships five tools. Coming soon: bulk_validate for processing lists in one call, subscribe_to_vat_changes for monitoring (so the agent can warn you if a known-good VAT later de-registers), and a vies_consultation_number tool that returns the audit token VIES issues when a requester VAT is configured.

If you have a specific use case the current tools don't cover, open an issue on GitHub — tool descriptions are tuned based on what people actually try, so feedback directly shapes the next release.