@onereason/svenska-dagar-mcp

MCP server exposing the Swedish public holiday and calendar API (sholiday.faboul.se) to Claude and other MCP clients.

Installation

Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "svenska-dagar": {
      "command": "npx",
      "args": ["-y", "@onereason/svenska-dagar-mcp"]
    }
  }
}

Restart Claude Desktop. The three tools below are then available in every conversation.

Tools

get_swedish_day

Returns calendar data for a single date.

| Parameter | Type | Description | |-----------|------|-------------| | year | integer | Year (1753–2100) | | month | integer | Month (1–12) | | day | integer | Day of month (1–31) | | sanitize | boolean | See Security — default true |

get_swedish_month

Returns calendar data for every day in a month.

| Parameter | Type | Description | |-----------|------|-------------| | year | integer | Year (1753–2100) | | month | integer | Month (1–12) | | sanitize | boolean | Default true |

get_swedish_year

Returns calendar data for every day in a year (~365 records). Prefer get_swedish_month when only a subset is needed.

| Parameter | Type | Description | |-----------|------|-------------| | year | integer | Year (1753–2100) | | sanitize | boolean | Default true |

Response fields

Each day record contains:

| Field | Type | Description | |-------|------|-------------| | datum | string | Date (YYYY-MM-DD) | | veckodag | string | Weekday name in Swedish | | vecka | string | ISO week number | | dag i vecka | string | Day of week (1 = Monday) | | arbetsfri dag | "Ja" | "Nej" | Work-free day | | röd dag | "Ja" | "Nej" | Public holiday (red day) | | namnsdag | string[] | Name days (namnsdagar) | | flaggdag | string | Flag day name, or "" | | helgdag | string | Holiday or named eve (e.g. "Juldagen", "Nyårsafton") — present only when applicable | | helgdagsafton | string | Eve before a red day (e.g. "Pingstafton") — present only when applicable | | klämdagen | "Ja" | Squeeze day (klämdagen) — present only when applicable | | dag före arbetsfri helgdag | "Ja" | Day before a work-free holiday — present only when applicable |

Security

All responses are sanitized before reaching the LLM by default:

• Field allowlist — unknown fields are dropped
• Injection scan — string values are checked against known prompt-injection patterns (ChatML tokens, role prefixes, markdown headers, etc.) and replaced with [redacted: suspicious content] if matched
• Length cap — strings longer than 100 characters are redacted
• Enum coercion — "röd dag" and "arbetsfri dag" are coerced to exactly "Ja" or "Nej"
• Hardcoded flags — presence-only fields (klämdagen, dag före arbetsfri helgdag) are always written as "Ja" regardless of what the API sends
• Non-object responses — if the upstream returns a string, array, or any non-object, an empty safe structure is returned instead of passing through raw content

Pass sanitize: false to receive the raw upstream response (useful for debugging).

Development

npm install        # install dependencies
npm run build      # compile TypeScript → dist/
npm test           # run unit + integration tests (requires network for API tests)

Running the server requires Node.js ≥ 18 (native fetch).
Running the tests requires Node.js ≥ 22.6 (--experimental-strip-types).

License

MIT