Holiday Calendar

Measured conclusion: Alive, not deep-tested. L2 outcome: not_attempted.

U.S. federal holidays with observed dates and business-day math. Example from an open-source kit.

Add to your agent

Copy this into your MCP client config:

{
  "mcpServers": {
    "Holiday Calendar": {
      "url": "https://starter.modernmustardseed.com/holidays",
      "transport": "streamable-http"
    }
  }
}

Measured tools (5)

• list_federal_holidays read-only

  List the eleven U.S. federal holidays for one calendar year (2021 through 2100): each holiday's name, its actual date and weekday, the date it is observed when it falls on a weekend (Saturday moves to the Friday before, Sunday to the Monday after), and the rule that sets it, from 5 U.S.C. 6103. Use it to answer which days federal offices close in a year.

  Parameters:

  • year (required) — integer — Calendar year, 2021 through 2100.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• next_federal_holidays read-only

  Find the next one to eleven U.S. federal holidays observed on or after a date, with each one's observed date and how many calendar days away it is. Without from_date it starts from today's date in America/New_York and says which date it used.

  Parameters:

  • count — integer — How many upcoming holidays to return, 1 to 11. Defaults to 1.
  • from_date — string — Start looking on this date, inclusive, written YYYY-MM-DD (for example 2026-11-26). Covers 2021 through 2100.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• check_business_day read-only

  Check whether a date is a U.S. business day (a weekday that is not an observed federal holiday). Returns the weekday, the holiday observed that day if any, and the business days just before and just after it.

  Parameters:

  • date (required) — string — The date to check, written YYYY-MM-DD (for example 2026-11-26). Covers 2021 through 2100.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• add_business_days read-only

  Move a number of U.S. business days forward or backward from a date, skipping weekends and observed federal holidays, for due dates, delivery windows and notice periods. The start date is not counted: 1 business day after a Friday is the next Monday, or Tuesday when that Monday is a holiday. Returns the resulting date and every holiday it skipped. Up to 1,000 business days either way.

  Parameters:

  • start_date (required) — string — The date to count from. It is not counted itself, written YYYY-MM-DD (for example 2026-11-26). Covers 2021 through 2100.
  • business_days (required) — integer — Business days to move, -1000 to 1000. Negative counts backward. 0 returns the start date if it is a business day, otherwise the next one.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• count_business_days read-only

  Count the U.S. business days between two dates, both dates included, leaving out weekends and observed federal holidays. Returns the business day count, the weekend days, and each holiday that fell in the span. Spans up to 3,660 calendar days.

  Parameters:

  • start_date (required) — string — First date of the span, counted if it is a business day, written YYYY-MM-DD (for example 2026-11-26). Covers 2021 through 2100.
  • end_date (required) — string — Last date of the span, counted if it is a business day, written YYYY-MM-DD (for example 2026-11-26). Covers 2021 through 2100.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

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