marketcal

An MCP server that gives AI agents correct trading-day and settlement math. LLMs are unreliable at "is the market open today?" and "what's the T+1 settlement date?" — this gets it exactly right, with no API key and no external calls.

Tool	Does
is_trading_day	Is a date a trading day? (weekend/holiday aware, with reason)
next_trading_day / previous_trading_day	Nearest trading day after/before a date
settlement_date	T+N settlement date (advance N trading days; T+1 is the modern default)
trading_days_between	Count trading days in an inclusive date range
market_holidays	List an exchange's holidays for a given year

Exchanges: NYSE, NASDAQ (US), LSE (London), XETRA (Frankfurt), GENERIC (weekends only).

Why it's correct

Holidays are computed from each exchange's rules — nth-weekday-of-month, Good Friday via the Gregorian Easter algorithm, and the exchange's weekend-observation rules (e.g. US: Saturday → Friday, Sunday → Monday; UK substitute days; XETRA closes Christmas Eve & New Year's Eve). No hardcoded date tables to rot — it stays right for any year.

Use it

npm install && npm run build && npm start
# or: npm run dev   (no build step)
npm run inspect      # try the tools in the MCP Inspector

Connect to Claude Desktop / Cursor:

{
  "mcpServers": {
    "marketcal": {
      "command": "npx",
      "args": ["-y", "mcp-marketcal"]
    }
  }
}

Then ask: "Using marketcal, what's the T+1 settlement date for a trade on 2026-07-02 on NYSE?" → 2026-07-06 (July 3 is the observed Independence Day holiday, July 4–5 is the weekend).

Notes & scope

• Covers full-day market closures. Early-close (half) days are not modelled in v0.1.
• All dates are calendar dates in YYYY-MM-DD (UTC), no intraday/timezone logic.
• settlement_date advances trading days (the standard settlement convention).
• Roadmap: more exchanges (TSX, Euronext, JPX, HKEX), early-close days, and a hosted HTTP + usage-billed tier (x402 / Stripe) for high-volume agents.

License

MIT