ProductivityMCP Registryremote5 toolsB · 73

Holiday Calendar MCP server

Name: Holiday Calendar
Author: modernmustardseed.com

com.modernmustardseed · Updated 15d ago

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

At a glance

Holiday Calendar is an MCP server in the Productivity category. It is hosted remotely and connects over HTTP, and declares no required credentials. It exposes 5 tools, including list_federal_holidays, next_federal_holidays and check_business_day. It scores B (73/100) on the MCP Skills Hub health score as of Oct 27, 2026.

Source 0

One-click install

VS Code VS Code Insiders Cursor

Opens your editor and pre-fills the config. Your editor will ask before adding it.

How to install Holiday Calendar in your AI client

Setup for Claude Code, Claude Desktop, Cursor, Codex, Windsurf, Cline and VS Code — copy-paste ready.

How to install Holiday Calendar in Claude CodeAnthropic's agentic CLI

Add the server

bash

claude mcp add --transport http holiday-calendar https://starter.modernmustardseed.com/holidays

2
Verify it's connected
bash
```
claude mcp list
```
Sharing it with your team?
Add `--scope project` to write it to .mcp.json in the repository root, which you can commit (with the secrets left as environment variables).
Use it in a session
Ask Claude to use the tools this server exposes (e.g. list_federal_holidays, next_federal_holidays, check_business_day). It discovers them automatically.

How to install Holiday Calendar in Claude DesktopDesktop app (MCP config)

Open your MCP config
macOS: ~/Library/Application Support/Claude/claude_desktop_config.json · Windows: %APPDATA%\Claude\claude_desktop_config.json

Add this server

json

{
  "mcpServers": {
    "holiday-calendar": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote",
        "https://starter.modernmustardseed.com/holidays"
      ]
    }
  }
}

Why the wrapper?
This is a remote (HTTP) server and Claude Desktop only launches local processes, so mcp-remote proxies the connection. It will open a browser window if the server needs OAuth.
Restart Claude Desktop
The tools appear under the 🔌 menu once the app reloads.

How to install Holiday Calendar in CursorAI-first code editor

Create / edit .cursor/mcp.json in your project

json

{
  "mcpServers": {
    "holiday-calendar": {
      "url": "https://starter.modernmustardseed.com/holidays"
    }
  }
}

Enable it
Cursor Settings → MCP → toggle the server on. Tools become available to the Composer/Agent.

How to install Holiday Calendar in Codex CLIOpenAI coding agent

Add to ~/.codex/config.toml

toml

[mcp_servers.holiday-calendar]
command = "npx"
args = ["-y", "mcp-remote", "https://starter.modernmustardseed.com/holidays"]

Why the wrapper?
Codex runs MCP servers as local processes, so mcp-remote bridges this HTTP endpoint to stdio.
Run Codex
Codex loads MCP servers from config.toml on startup and exposes their tools to the agent.

How to install Holiday Calendar in WindsurfCodeium's agentic IDE

Edit ~/.codeium/windsurf/mcp_config.json

json

{
  "mcpServers": {
    "holiday-calendar": {
      "serverUrl": "https://starter.modernmustardseed.com/holidays"
    }
  }
}

Reload
Windsurf → Cascade → refresh MCP servers. Cascade can now call the tools.

How to install Holiday Calendar in ClineVS Code autonomous agent

Open Cline → MCP Servers → Configure
Adds to cline_mcp_settings.json.

Add the server

json

{
  "mcpServers": {
    "holiday-calendar": {
      "type": "streamableHttp",
      "url": "https://starter.modernmustardseed.com/holidays"
    }
  }
}

How to install Holiday Calendar in VS CodeCopilot / MCP support

Create .vscode/mcp.json

json

{
  "servers": {
    "holiday-calendar": {
      "type": "http",
      "url": "https://starter.modernmustardseed.com/holidays"
    }
  }
}

Start it
VS Code shows a ▶ Start action above the server entry. Agent mode (Copilot Chat) can then use the tools.

What tools does Holiday Calendar expose? (5)

Read from the live server. Click any tool for its input schema.

list_federal_holidaysList 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.
next_federal_holidaysFind 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.
check_business_dayCheck 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.
add_business_daysMove 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.
count_business_daysCount 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.

What the code can do

This is a remote server — nothing is installed or run on your machine, so there is no local code to analyze. What it can reach is described above: your requests go to the provider's host.

Before you install

Signals gathered from the source repo and package registry — not a safety verdict.

What it can reach

Third-party hosted service — Your requests and any data in them are sent to starter.modernmustardseed.com.
No local execution — Nothing is installed or run on your machine.

Last commit 15 days ago — Actively maintained.
Repository created 16 days ago — Very new project with little track record yet.
0 GitHub stars — Very little community usage so far.

Client compatibility

Claude Code: NativeClaude Desktop: Via mcp-remoteCursor: NativeCodex CLI: Via mcp-remoteWindsurf: NativeCline: NativeVS Code: Native

Health score

B · 73

Maintenance, adoption, transparency and packaging — not a safety audit. How this is calculated

Maintenance30%100%
Last commit 15 days ago.
Adoption20%0%
0 stars.
Transparency20%100%
4/4: ✓ public source repo, ✓ declared license, ✓ documentation, ✓ discoverable tool list.
Provenance15%75%
Links to its own repository; package linkage unverified.
Packaging15%75%
Remote endpoint; authentication requirements not declared.

Documentation

Full README

Small Business MCP Starter Kit by Modern Mustard Seed

Ship a remote MCP connector for Claude that is built to pass Anthropic's directory review on the first try.

This kit is the set of patterns Modern Mustard Seed uses for the connectors it runs in production, pulled out into a clean Next.js project you can fork:

A route template on Next.js App Router and `mcp-handler`, serving Streamable HTTP at one URL per connector, with no redirect.
Tool conventions enforced at load time: a title, readOnlyHint or destructiveHint on every tool, snake_case names of 64 characters or fewer, and descriptions that describe instead of steer. Break a rule and pnpm test fails, long before a reviewer sees it.
Specific error messages instead of "Bad Request", and output size caps under Claude's limits.
Rate limiting built for Claude's shared egress range. Every claude.ai user arrives from 160.79.104.0/21, so nothing is keyed by IP and nothing returns HTTP 429.
An SSRF-safe fetch for any tool that reads a URL a user supplied, with tests that prove a listening loopback server receives zero requests.
An eval harness that runs real prompts against your live URL, with no model and no API key.
Docs, privacy, terms and support page templates plus /.well-known/security.txt, all driven by one config file.
A submission checklist mapped to the directory form's 10 steps and its seven policy acknowledgments, with every rule linked to Anthropic's documentation.
A worked example: a U.S. federal holiday and business-day calendar with five read-only tools that passes all 35 of its own evals.

MIT licensed. Built by Modern Mustard Seed.

Working demo

The example connector runs live, deployed from this repository with no changes:

Connector URL: https://starter.modernmustardseed.com/holidays (add it in Claude under Customize > Connectors > Add custom connector)
Docs page reviewers read: https://starter.modernmustardseed.com/docs/holidays
Privacy, terms and support: https://starter.modernmustardseed.com/privacy, /terms, /support
Official MCP Registry entry: com.modernmustardseed/holiday-calendar

Run the evals against it yourself: node eval/holidays.eval.mjs https://starter.modernmustardseed.com

Quickstart: 10 minutes

You need Node 22.6 or later, pnpm, and a Vercel account (any host that runs Next.js works).

1. Make your copy. (1 minute)

gh repo create my-connector --template ModernMustardSeed/small-business-mcp-starter --public --clone
cd my-connector
pnpm install

Or select Use this template on GitHub.

Excerpt — the full document is on GitHub.

Alternatives to Holiday Calendar

Maintain Holiday Calendar? Add a badge to your README

Shows its health grade, and links readers to install steps for every client.

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