skanfirmy.pl — MCP server

A free, stateless MCP (Model Context Protocol) server that lets AI agents verify Polish companies and validate EU VAT numbers directly from official government registers. No key and no registration for the lookups; per-IP rate limits apply (see Limits and personal data).

• Endpoint: https://skanfirmy.pl/mcp (JSON-RPC 2.0 over Streamable HTTP)
• 14 tools: 9 lookups and calculators combining the VAT Register (Ministry of Finance), KRS (Ministry of Justice), REGON (Statistics Poland / GUS) and VIES (European Commission), plus 5 tools for the optional change monitoring, which need an API key.
• Also usable as plain REST for crawlers/agents that can't speak MCP.

Made by Bartosz Kuć — the same person behind skanfirmy.pl and the otwarteAPI.pl catalog of Polish & EU public APIs.

Tools

Tool	What it does
sprawdz_nip	VAT status (Biała Lista) + KRS data for a company by NIP
sprawdz_lista_nip	Bulk lookup of up to 30 NIPs in one call (MF VAT Register)
sprawdz_regon	REGON registry data (GUS) by NIP; for sole traders and other natural persons only name, legal form, entity type, town and activity status
sprawdz_vies	Validate an EU VAT number via VIES (European Commission)
sprawdz_rachunek	Is a bank account on the VAT White List for a given NIP
generuj_mikrorachunek	Individual tax micro-account (PIT/CIT/VAT) from a NIP; the formula for a PESEL is in the tool description, to compute locally
szukaj_pkd	Search the PKD 2025 business-activity classification
oblicz_odsetki	Statutory / commercial (B2B) late-payment interest calculator
szukaj_katalog_api	Search otwarteAPI.pl — a catalog of other public PL/EU APIs

Monitoring tools (need a skanfirmy API key, which you get after confirming a sign-up at skanfirmy.pl/monitoring): observe_nip, unobserve_nip, list_observations, changes_since, set_webhook.

Limits and personal data

• Rate limits per IP address. MCP: at most 60 requests per 10 seconds, then HTTP 429 with a JSON-RPC error (error.data.contact) for 10 seconds. REST endpoints: at most 20 requests per 10 seconds, then HTTP 429 for 10 seconds. The service is meant for single lookups started by users or their agents, not for bulk data harvesting.
• Source limits. The Ministry of Finance White List API has its own daily limits (search: 100 queries a day, up to 30 NIPs each), shared by all users of the service. When they run out, lookups answer HTTP 503 until the next day.
• Sole traders and other natural persons (entities without a KRS number, and civil partnerships) get minimised data (GDPR): name, NIP, VAT status, town and the number of White List accounts. No REGON number, address, registration date, PKD codes or list of account numbers. To check one specific account, use sprawdz_rachunek (REST: POST /rachunek).
• Numbers restricted from presentation. Data for some numbers is not presented (a data-protection procedure). The answer is then restricted: true with a fixed sentence and a link to the Ministry of Finance search, with no data and no fields about validity, VAT status or presence in the register. Send the user to the official search.

Connect

Any MCP client that supports remote (Streamable HTTP) servers — point it at:

https://skanfirmy.pl/mcp

Claude Desktop / stdio-only clients — bridge with mcp-remote:

{
  "mcpServers": {
    "skanfirmy": {
      "command": "npx",
      "args": ["-y", "mcp-remote", "https://skanfirmy.pl/mcp"]
    }
  }
}

Raw JSON-RPC (no MCP client needed):

# list tools
curl -s https://skanfirmy.pl/mcp \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'

# check a company by NIP
curl -s https://skanfirmy.pl/mcp \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"sprawdz_nip","arguments":{"nip":"5261040828"}}}'

Plain REST (no MCP)

For agents/crawlers that just want a URL:

• GET https://skanfirmy.pl/nip/{nip} — VAT + KRS
• GET https://skanfirmy.pl/nips/{comma,separated,nips} — bulk (≤30)
• GET https://skanfirmy.pl/regon/{nip} — REGON registry data
• GET https://skanfirmy.pl/vies/{country}/{number} — EU VAT (VIES)
• POST https://skanfirmy.pl/rachunek — is one bank account on the White List for a NIP

Add ?format=json for JSON. Full docs: skanfirmy.pl/llms.txt, OpenAPI: skanfirmy.pl/openapi.yaml.

Claude Agent Skill

Prefer a drop-in Agent Skill? skill/ holds verify-polish-company — a single SKILL.md that teaches Claude Code, the Claude apps or the Agent SDK when and how to call the endpoints above (no key, nothing to run beyond ordinary HTTP):

cp -R skill ~/.claude/skills/verify-polish-company

See skill/README.md for details.

Data sources

VAT Register / Biała Lista (Ministry of Finance), KRS (Ministry of Justice), REGON / BIR (Statistics Poland — GUS), VIES (European Commission). Independent project — not affiliated with any of them. What the service stores and for how long is described in its privacy policy.

Author

Bartosz Kuć · skanfirmy.pl · github.com/bartosz-kuc · linkedin.com/in/bartosz-kuc · cal.com/bartosz-kuc

License

MIT © Bartosz Kuć. This repository documents the hosted server and holds its MCP registry manifest; the server itself runs at https://skanfirmy.pl/mcp.