Openworkdays

solvohq/openworkdays

A zero-signup business day calculator you can call directly from Claude or any MCP client. It exposes a single tool that handles three operations: add or subtract working days from a date, count business days between two dates, or check if a date is a business day. You pass your own holiday list as parameters, so it works for any calendar without needing a pre-built database. The entire thing runs as a stateless HTTP endpoint with no authentication, which makes it useful when you need date math in an agent workflow but don't want to deal with API keys or trust an LLM to count weekdays correctly. Self-hostable as two dependency-free Node functions.

tool: 1
transport: HTTP
last updated: May 17, 2026

View on GitHub

Install

From registry metadata

$ npx add-mcp https://openworkdays.vercel.app/api/mcp --name openworkdays

Run in your terminal. add-mcp asks which agents to add it to (Claude Code, Codex, Cursor and more). Add -g to install it for every project.

Review the command, arguments and environment values before installing. MCP servers run with your local permissions.

Other ways

Claude Code

$ claude mcp add --transport http openworkdays https://openworkdays.vercel.app/api/mcp

Run in your terminal. Add --scope user to make it available in every project.

Tools

Verified live · 1 tools

Verified live against the running server on Nov 6, 2026.

businessdaysBusiness-day date math. Three modes inferred from params: add (start+days -> the date N business days away, negative days = before), diff (start+end -> count of business days between, inclusive of both endpoints), is (date -> is it a business day). Optional weekend (default sa...6 params

Business-day date math. Three modes inferred from params: add (start+days -> the date N business days away, negative days = before), diff (start+end -> count of business days between, inclusive of both endpoints), is (date -> is it a business day). Optional weekend (default sa...

Parameters* required

datestring

Date YYYY-MM-DD to test (is mode)

daysinteger

Business days to add (add mode); negative subtracts

endstring

End date YYYY-MM-DD (diff mode)

holidaysstring

Comma list of YYYY-MM-DD dates treated as non-working

startstring

Start date YYYY-MM-DD (add & diff modes)

weekendstring

Comma list of weekend days, e.g. "sat,sun" (default sat,sun)

Readme

OpenWorkdays

A zero-signup business-day / working-day date-arithmetic API. No account, no API key — one GET request.

Add or subtract working days, count business days between two dates, or test whether a date is a business day — with your own holiday list. Pure UTC date math, returned as JSON. Built so autonomous AI agents get a deterministic date endpoint — an agent has no human to do a signup, and LLMs are measurably unreliable at date arithmetic.

Live: https://openworkdays.vercel.app

Quick start

curl "https://openworkdays.vercel.app/api/businessdays?start=2026-05-15&days=5"

Sample response:

{
  "mode": "add",
  "start": "2026-05-15",
  "days": 5,
  "result": "2026-05-22",
  "resultWeekday": "fri",
  "startIsBusinessDay": true,
  "weekend": ["sat", "sun"],
  "holidaysApplied": 0,
  "engine": "date-utc-v0.1",
  "computedAt": "2026-05-17T00:00:00.000Z"
}

Any error returns JSON with an error key and an appropriate HTTP status (400 bad params, 429 rate limited, 405 wrong method).

The three modes

The endpoint is always GET /api/businessdays. The mode is inferred from the params you pass.

View the full README on GitHub

Details

Repository: github.com/solvohq/openworkdays
Transport: HTTP
Registry: MCP registry, active
Tools verified: Nov 6, 2026