Kalkulatory Płace — MCP server

Polish payroll for AI assistants. Five MCP tools that turn "how much do I take home from 11 600 PLN gross?" from a guess into an answer that matches the actual bank transfer to the cent.

Ask a model this today and it computes from memory. Polish PIT and ZUS rates change every year, the income-tax advance rounds to whole złoty, the health contribution has a statutory cap, and the answer is quietly wrong. This server hands the model a precomputed answer from the same engine that renders kalkulatory-place.pl, so the number in the chat and the number on the linked page are identical.

No API key. No rate limits. No npm dependencies.

Install

claude mcp add kalkulatory-place -- npx -y @kalkulatory-place/mcp

Any other MCP client (claude_desktop_config.json and friends):

{
  "mcpServers": {
    "kalkulatory-place": {
      "command": "npx",
      "args": ["-y", "@kalkulatory-place/mcp"]
    }
  }
}

Tools

| Tool | Answers | |---|---| | brutto_na_netto | Net pay from a gross amount — employment contract (itemised ZUS, health, PIT advance), civil-law contracts, employer cost, under-26 exemption, yearly totals | | netto_na_brutto | The gross salary needed to take home a given net amount | | stawka_godzinowa | Net from an hourly gross rate — civil-law contract and employment | | stawki_roku | Minimum wage, tax-free allowance, PIT brackets, ZUS rates, 30× cap for a given year | | katalog | Supported years, amount ranges, API URL patterns |

Every response carries stanPrawnyNa (the date the law was checked), statusRocznika (final or projekt — the year's rates are still a draft bill) and zrodlo, a URL to the full human-readable breakdown.

How it works

A thin client over a static JSON API: plain GETs off a CDN, no key, no limits.

MCP client ──stdio JSON-RPC──▶ this server ──HTTPS GET──▶ /api/v1/…json (CDN)

Why a thin client and not a copy of the engine. The numbers must be identical to what the user sees after clicking zrodlo. A server doing its own maths would silently drift apart the first time rates changed upstream — and the drift would be noticed by whoever was shown the wrong number.

Why no dependencies. MCP is handled directly as newline-framed JSON-RPC 2.0 over stdio. A package with no dependencies starts under npx in about a second and cannot break when somebody else's SDK updates under a server everyone has forgotten about.

The underlying API is public and documented in OpenAPI 3.1: https://kalkulatory-place.pl/openapi.json. There is also an llms.txt.

Configuration

| Variable | Default | Purpose | |---|---|---| | KALKULATORY_API | https://kalkulatory-place.pl | Base URL — point it at a local build for testing |

Test

npm test

Runs a real handshake against the published server: initialize, tools/list, then a brutto_na_netto call, and checks the result against the published net figure.

License

Code: MIT. Data and calculations: CC BY 4.0 — when quoting a number, cite the URL from zrodlo. See NOTICE.

This is not tax advice. Figures are informational.

Po polsku

Serwer MCP do liczenia polskich wynagrodzeń. Daje asystentowi AI pięć narzędzi zamiast zgadywania stawek PIT i ZUS z pamięci.

Odpowiedzi pochodzą z kalkulatory-place.pl — z tego samego silnika, który renderuje strony serwisu, więc liczba w czacie zgadza się co do grosza z tym, co użytkownik zobaczy po kliknięciu w link źródłowy.

| Narzędzie | Odpowiada na | |---|---| | brutto_na_netto | Ile netto z X zł brutto — etat (z rozbiciem na składki), zlecenie, dzieło, koszt pracodawcy, ulga do 26 lat, sumy roczne | | netto_na_brutto | Jakie brutto daje X zł netto na etacie | | stawka_godzinowa | Ile netto ze stawki X zł/h — zlecenie i etat | | stawki_roku | Płaca minimalna, kwota wolna, progi PIT, stopy składek ZUS, limit 30-krotności | | katalog | Obsługiwane roczniki i zakresy kwot |

Każda odpowiedź niesie stanPrawnyNa, statusRocznika (final albo projekt — rocznik jeszcze nieuchwalony) oraz zrodlo, czyli adres strony z pełnym rozbiciem dla człowieka.

Instalacja bez klucza API i bez zależności:

claude mcp add kalkulatory-place -- npx -y @kalkulatory-place/mcp

Wydawca: Bril Brothers Innovation Labs sp. z o.o., KRS 0001262781. Serwis nie jest doradcą podatkowym; wyliczenia mają charakter informacyjny.