About this API
This is the catalog's one flagship entry — the author's own product. Unlike the rest of the catalog (plain REST APIs), this is a real MCP (Model Context Protocol) server that an agent can call as a "tool," not just read as data. It combines data from the VAT Register (Ministry of Finance), KRS (Ministry of Justice), and GUS in a single call, and can now also search this very catalog via the szukaj_katalog_api tool.
Frequently asked questions
Do I need an API key?
No, the server is fully public and free — no registration, no key, no limits other than those imposed by the source registries themselves (e.g. 100 requests/day per IP on the VAT Register).
How is this different from a plain REST API?
Standard JSON-RPC 2.0 (initialize, tools/list, tools/call) over the MCP protocol — an agent first discovers the available tools, then calls the one it needs with specific arguments, instead of needing to know a fixed URL shape in advance.
What tools are available?
sprawdz_nip, sprawdz_vies, sprawdz_rachunek, generuj_mikrorachunek, szukaj_pkd, oblicz_odsetki, and szukaj_katalog_api — the last one searches this very catalog, otwarteAPI.pl.
Who runs this API?
The same person who runs otwarteAPI.pl. Full documentation and the tool list are available at skanfirmy.pl/mcp and in skanfirmy.pl/llms.txt.