Power your agent
The publisher's own URL. Not a PlugMCP endpoint.
Host a copy with our keys and logs.
https://openworkdays.vercel.app/api/mcpThe Claude button above opens Claude with the name and URL filled in. You still confirm it there.
claude mcp add --transport http io.github.solvohq-openworkdays https://openworkdays.vercel.app/api/mcpRun in a terminal.
{ "mcpServers": { "io.github.solvohq-openworkdays": { "command": "npx", "args": [ "-y", "mcp-remote", "https://openworkdays.vercel.app/api/mcp" ] } }}claude_desktop_config.json
Remote URL or a command on your machine? How the two installs differ
Run on PlugMCP
A new server you create. It is not this listing's official endpoint. Use the publisher install when you want their URL and their credentials.
LaunchFrom the publisher
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.
Zero-signup business-day date-math API: add days, count days between dates, is-business-day.
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 endpoint is always GET /api/businessdays. The mode is inferred from the
params you pass.
add — add/subtract working daysParams: start=YYYY-MM-DD, days=N (integer, +/- ok, |N| <= 10000),
optional weekend=, optional holidays=.
curl "https://openworkdays.vercel.app/api/businessdays?start=2026-05-15&days=5"
N=0 returns start unchanged (even if start is itself non-working).
diff — count business days between two datesParams: start=YYYY-MM-DD, end=YYYY-MM-DD, optional weekend=, optional
holidays=. Inclusive of both endpoints. Result is negative if
end < start.
curl "https://openworkdays.vercel.app/api/businessdays?start=2026-05-15&end=2026-06-15&holidays=2026-05-25"
is — is this date a business day?Params: date=YYYY-MM-DD, optional weekend=, optional holidays=.
curl "https://openworkdays.vercel.app/api/businessdays?date=2026-05-16"
Returns isBusinessDay plus a reason of "weekend", "holiday", or null.
weekend (default sat,sun) — comma list. Tokens are case-insensitive
from {sun,mon,tue,wed,thu,fri,sat}, or numeric 0-6 where 0=Sunday …
6=Saturday (matches JS getUTCDay()). Cannot mark all 7 days as weekend.holidays — comma list of YYYY-MM-DD dates treated as non-working
(max 1000). Strictly validated.Errors are JSON with an error key:
400 — bad/missing params (missing start, invalid days (must be integer),
invalid weekend token, invalid holiday date, invalid date,
specify a mode (includes a usage object), …)429 — rate limited (Retry-After header + retryAfterSec)405 — wrong HTTP method (only GET/OPTIONS allowed)const base = "https://openworkdays.vercel.app";
const r = await fetch(
base + "/api/businessdays?start=2026-05-15&days=5"
);
const out = await r.json(); // { mode:"add", result:"2026-05-22", resultWeekday:"fri", ... }
OpenWorkdays is also a remote MCP server, so an agent can call it as a tool with no signup, no API key, no OAuth.
https://openworkdays.vercel.app/api/mcpapplication/json response — no sessions, no SSE)businessdays — the mode (add / diff /
is) is inferred from which args you pass, returning the same JSON as the
REST endpoint (also as structuredContent)Drop this into any MCP client config (Claude Desktop, Cursor, or any client that speaks the Streamable HTTP transport):
{ "mcpServers": { "openworkdays": { "url": "https://openworkdays.vercel.app/api/mcp" } } }
Quick smoke test:
curl -s -X POST https://openworkdays.vercel.app/api/mcp \
-H 'Content-Type: application/json' \
-d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"businessdays","arguments":{"start":"2026-05-15","days":5}}}'
Over MCP, an upstream error comes back as a tool result with isError: true.
Every public business-day API gates behind an account or API key:
workingdays.org is test-only / subscription;
API Ninjas and Holiday API
need keys; timeanddate is a $299 product;
the RapidAPI business-day APIs need a RapidAPI key; Microsoft's "Calculate
Working Day" connector is Power-Platform-framework-gated and UK-bank-holidays
only. OpenWorkdays is a single anonymous GET — no signup, no key. That is
especially useful to autonomous agents, which have no human in the loop to
complete a signup. And because LLMs are measurably unreliable at date
arithmetic, an agent needs a deterministic endpoint rather than guessing.
holidays= list you care about.The entire API is two single zero-dependency Node serverless functions:
api/businessdays.js (REST) and api/mcp.js
(remote MCP). No npm install, no deps at all. Deploy the folder to Vercel
(zero-config /api detection) or drop the handlers into any Node serverless
runtime.
git clone https://github.com/SolvoHQ/openworkdays
cd openworkdays
npx vercel --prod
MIT — see LICENSE.
© 2026 MCP Directory.
Zero-signup business-day date-math API: add days, count days between dates, is-business-day.
{ "mcpServers": { "io.github.solvohq-openworkdays": { "url": "https://openworkdays.vercel.app/api/mcp", "headers": {} } }}Tools
No tool list yet. Remote servers get one after the first health check.
FAQ
Copy the http config for Cursor, Claude Desktop, Claude Code, or VS Code on this page. It uses the publisher's install, not a PlugMCP proxy.
No required environment variable is listed on this record.
Openworkdays is reached over HTTP.
Last checked 2026-11-09. Zero-signup business-day date-math API: add days, count days between dates, is-business-day.