pl-holidays-mcp

Local MCP server for Polish public holidays and business-day arithmetic. Wraps the open Nager.Date holiday database and adds bookkeeping-friendly business-day math on top.

Part of the honest-mcp family of small, auditable, local-first MCP servers.

Why

Every Polish accountant, JDG owner, or HR person has this problem:

• "Payment term is 14 dni roboczych from invoice date — what's the actual due date?"
• "Is the client's 'termin płatności 2026-05-01' the same as next_business_day(2026-05-01)? (No — that's Święto Pracy.)"
• "Deadline for JPK_V7 is the 25th — but 2026-04-25 is a Saturday, does it slip to Monday?"

This server hands both raw holiday data and business-day arithmetic to your AI. No more spreadsheet calendars.

Supports any country Nager.Date covers (110+), but the API defaults to Poland and the bookkeeping angle is Poland-centric.

Features

Six tools:

• list_holidays — all public holidays in a given year
• is_holiday — is this specific date a public holiday?
• is_business_day — is this date Mon–Fri and not a holiday? Includes reason (weekend / holiday / business_day)
• count_business_days — inclusive business-day count between two dates
• add_business_days — start_date + N business days = ? (N can be negative)
• next_holidays — upcoming N holidays from a given date

Data source

• Endpoint: date.nager.at/api/v3
• No API key
• MIT-licensed holiday data
• In-memory year cache — one round trip per year per session

Requirements

• Python 3.10+

Setup

git clone https://github.com/bartosz-kuc/pl-holidays-mcp.git
cd pl-holidays-mcp
python3 -m venv venv
./venv/bin/pip install -r requirements.txt

Register with Claude Code:

claude mcp add pl-holidays /absolute/path/to/venv/bin/python /absolute/path/to/server.py

Claude Desktop claude_desktop_config.json:

{
  "mcpServers": {
    "pl-holidays": {
      "command": "/absolute/path/to/venv/bin/python",
      "args": ["/absolute/path/to/server.py"]
    }
  }
}

Example usage

"Invoice issued today with 14 working-day payment term — when is it due?"

add_business_days(start_date="2026-07-22", days=14) → the due date, skipping weekends and Polish public holidays.

"How many working days between 2026-04-01 and 2026-04-30?"

count_business_days(from_date="2026-04-01", to_date="2026-04-30")

"Is May 1st 2026 a business day in Poland?"

is_business_day(date="2026-05-01") → false, reason: holiday (Święto Pracy).

Data flow

Your AI client
     ↕  MCP stdio
This server (Python, on your machine)
     ↕  HTTPS
date.nager.at (Nager.Date open holiday DB)

No cloud middle for anything but the initial holiday-date fetch. No telemetry.

Author

Bartosz Kuć — Warsaw-based developer, JDG owner running skanfirmy.pl.

• GitHub: https://github.com/bartosz-kuc

• Email: firma@bartosza.pl

Consulting

Available for consulting on Polish tax and business integrations (KSeF, GUS/NFZ/GIOŚ APIs, mBank data), MCP server design, and AI-assisted tooling for JDGs and small teams. See skanfirmy.pl/uslugi for productized packages (audit 3k PLN, setup 8-15k PLN, retainer 2-4k PLN/mo), or reach out via email.

License

MIT — see LICENSE.

Related

• Part of the honest-mcp family — see the family index.