🇨🇭 Part of the Swiss Public Data MCP Portfolio

This is a private project. It is independent of any employer or institutional affiliation and represents no official position of any authority.

📅 swiss-holidays-mcp

A Swiss holiday calendar for AI agents — public holidays, school holidays and long weekends for all 26 cantons, with cross-cantonal comparison. School holidays are differentiated by Schulart (school type), which matters more than it first appears. No API key required.

🇩🇪 Deutsche Version

Overview

swiss-holidays-mcp is a Swiss holiday calendar for AI assistants like Claude — public holidays, school holidays and long weekends for all 26 cantons, no API keys required. Public holidays are cantonal (Berchtoldstag, Fronleichnam & co. differ by canton, not just the federal minimum). School holidays are set cantonally, sometimes at district level, and — in six cantons — separately per school type. A single federal calendar does not exist; anyone planning across cantonal borders is otherwise reduced to opening 26 PDF pages.

The server covers two thematic clusters: public holidays / long weekends and school holidays (with Schulart differentiation). Each cluster maps to a group of purpose-built tools that translate raw agency data into clean, provenance-tagged JSON responses. All data comes from the OpenHolidays API (CC BY 4.0) and Nager.Date (MIT).

Mnemonic: A duplicate in Swiss school data is usually a school type in disguise. The underlying API publishes the same holiday period several times when a canton differentiates by school type. That looks like duplicated data and invites naive de-duplication — which would destroy exactly the distinction a school authority needs.

Anchor demo query: "In which weeks of 2026 are the compulsory schools of Zurich, Zug and Aargau simultaneously on holiday — and how many overlapping days does each pair share?" → This exercises find_common_free_window, compare_school_holidays and list_school_types in a single conversation, and answers a question that recurs every planning cycle in inter-cantonal coordination. → More use cases by audience →

Demo

Features

• 🏫 School holidays — periods per canton and date range, differentiated by Schulart (VS / MS / BS / EO)
• 🎌 Public holidays — cantonal holiday sets, not just the federal minimum (Berchtoldstag & friends)
• 🔍 Date check — is a given date a school or public holiday in a canton?
• 🔗 Cross-cantonal comparison — pairwise overlap matrix of holiday days between cantons
• 🪟 Common free windows — date ranges where all listed cantons are simultaneously on holiday
• 🌉 Long weekends & bridge days — computed from federal public holidays (Nager.Date)
• 🏘️ Local & municipal holidays — district- and municipality-level specifics such as Zurich's Sechseläuten and Knabenschiessen, with a scope marker so they are never mistaken for canton-wide
• 📆 iCal / ICS export — a canton's holidays for a year as a ready-to-import .ics calendar
• 🔖 Holiday feed resource — holidays://<canton>/<year> MCP resource with a Markdown summary
• 📌 "Is today a holiday?" — one-call convenience for the everyday question
• 🩺 Source health — reachability and latency of both upstreams, always evaluable
• 🔑 No authentication required — both data sources are publicly accessible
• ☁️ Dual transport — stdio for Claude Desktop, Streamable HTTP/SSE for cloud deployment
• 🧾 Provenance on every response — live_api | cached | degraded, never a silent empty list

Data Sources

Both sources are publicly accessible, no authentication required. Attribution required: OpenHolidays (CC BY 4.0) and Nager.Date must be cited as the source when using their data.

Tools

Resources

All tools carry the full annotation set — readOnlyHint: true, destructiveHint: false, idempotentHint: true, openWorldHint: true (they reach an external API). No tool writes anywhere. Inputs are schema-validated (canton codes against the 26 known cantons, dates as YYYY-MM-DD, year bounded, language/school_type whitelisted).

Example Use Cases

🛡️ Safety & Limits

Architecture

This server uses Architecture A (live API only, with in-memory cache).

                    ┌──────────────────────────┐
   Claude / any ───▶│  swiss-holidays-mcp      │
   MCP host         │  (MCPServer · 13 tools)  │
                    └────────┬─────────────────┘
                             │  retry 2s/4s/8s · 12h cache
                    ┌────────┴─────────┐
                    ▼                  ▼
          OpenHolidays API        Nager.Date
          (CC BY 4.0)             (MIT)
          cantons · Schularten    long weekends
          school + public         bridge days

Rationale (verified live on 2026-07-19):

• All ten documented OpenHolidays endpoints answered HTTP 200 with plausible payloads; /Subdivisions?countryIsoCode=CH returns exactly 26 cantons, matching the official count.
• No public bulk dump could be verified at build time (openpotato/openholidays.data raw access returned 404), so Architecture B was not available.
• Holiday tables change a handful of times per year, so a 12-hour in-memory TTL removes almost all upstream load without risking staleness.

Consequences:

• Every response carries provenance (live_api | cached | degraded).
• Upstream failure yields a degraded envelope with an explanatory note, never a silent empty list.
• source_status always returns an evaluable health report.