Kalkulatory Place MCP server

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 (claudedesktopconfig.json and friends):

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

Tools

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: . There is also an llms.txt.

Configuration

Test

npm test

Runs a real handshake against the published server: initialize, tools/list, then a bruttonanetto 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.

Shortened. The full README is on GitHub.