Holiday Calendar

Name: Holiday Calendar
Author: ModernMustardSeed

by ModernMustardSeedversion 1.0.1i★ 0iRuns in the cloud

Registry namecom.modernmustardseed/holiday-calendar

How to install

What it does

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

Connects Runs in the cloud
Account or key No key needed
Category Docs, sheets & office work

Install

Pick the AI app you use, then copy the settings.

Passed 5/5 checks · What you ask goes through the maker’s server (starter.modernmustardseed.com)

First: which AI do you use?

ClaudeWeb · app · phoneChatGPTWebClaude CodeTerminalCursorCode editorVS CodeCode editorOtherOther apps

Pick your app and the steps appear below.

Works with Claude · about 2 min

No key, nothing to install · Set it up once on claude.ai or the desktop app, then use it in chat · free accounts can add 1 · on Team/Enterprise an Owner adds it

Open Claude’s Connectors page
CustomizeConnectors
Done
Click “+ Add” → “Add custom connector” and fill in these 2 fields
Copy each value into the field with the same name in Claude, then click Continue
Name · NameHoliday Calendar
Remote MCP server URL · Addresshttps://starter.modernmustardseed.com/holidays
Leave Authentication as Claude detected it, then click Add
Done
Turn it on in a chat
+ConnectorsHoliday Calendar
Done
Try it
Use Holiday Calendar and tell me what you can do for me, then show me one thing
✓ If Claude says it is using Holiday Calendar or shows a Holiday Calendar tool in the answer, you are connected

Menu names checked against Anthropic’s help page on Nov 11, 2026 · your screen may differ slightly by app version

Works with ChatGPT on business plans only

ChatGPT Business, Enterprise or Edu on the web, added by a workspace admin or owner · On Free, Plus or Pro: your ChatGPT plan cannot connect MCP yet

Open ChatGPT’s add-MCP page on the web
Plugins+Add custom MCP server
Done
Fill in the name and address
Enter a name, paste the address under Connection, tick the risk warning and click Create as a plugin
Name · NameHoliday Calendar
Connection · Addresshttps://starter.modernmustardseed.com/holidays
Done
Pick Holiday Calendar in a chat
Start a new chat and pick Holiday Calendar from your plugins before typing
Done
Try it
Use Holiday Calendar and tell me what you can do for me, then show me one thing
✓ If ChatGPT says it is using Holiday Calendar or shows a Holiday Calendar tool in the answer, you are connected

Menu names checked against OpenAI’s help page on Nov 11, 2026 · your screen may differ slightly by app version

Works with Claude Code · about 2 min

No key, nothing to install

Open Terminal
Mac: press Command+Space and type Terminal · Windows: open PowerShell
Done

Paste this command and press Enter

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

Done

Type /mcp in Claude Code
You should see Holiday Calendar listed as connected
Done
Try it
Use Holiday Calendar and tell me what you can do for me, then show me one thing
✓ If Claude Code says it is using Holiday Calendar or shows a Holiday Calendar tool in the answer, you are connected

Menu names checked against Anthropic’s help page on Nov 11, 2026 · your screen may differ slightly by app version

Works with Cursor · about 2 min

No key, nothing to install

Click this button to open Cursor
Open in Cursor
Cursor asks you to confirm; click Install
Done
Open the AI chat in Cursor in Agent mode
Done
Try it
Use Holiday Calendar and tell me what you can do for me, then show me one thing
✓ If Cursor says it is using Holiday Calendar or shows a Holiday Calendar tool in the answer, you are connected

Menu names checked against Cursor’s help page on Nov 11, 2026 · your screen may differ slightly by app version

Works with VS Code · about 2 min

No key, nothing to install

Click this button to open VS Code
Open in VS Code
VS Code asks you to confirm; click Install
Done
Open the AI chat in VS Code in Agent mode
Done
Try it
Use Holiday Calendar and tell me what you can do for me, then show me one thing
✓ If VS Code says it is using Holiday Calendar or shows a Holiday Calendar tool in the answer, you are connected

Menu names checked against VS Code’s help page on Nov 11, 2026 · your screen may differ slightly by app version

Other apps that use MCP, such as Windsurf, Zed or Gemini CLI, each add servers differently. See how in the app list.

See every app that uses MCP →

Address for apps that connect over the web

Addresshttps://starter.modernmustardseed.com/holidays

JSON settings are under “For developers” below

Stuck? Ask people who use Holiday Calendar💬 Discussion →

For developers: Terminal commands and JSON settings

Over the web

Claude Code

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

Cursor (~/.cursor/mcp.json)

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

VS Code (mcp.json)

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

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

At a glance

GitHub stars i: 0
Downloads per weeki: Not on npm/PyPI
Verified domain: ✓ modernmustardseed.com
Licence i: MIT
Connection: Runs in the cloud
Transport: streamable-http
Latest versioni: 1.0.1
Categoryi: Docs, sheets & office work
Published to registryi: Oct 12, 2026
Code last changedi: Oct 30, 2026
Maker: ModernMustardSeed
Repo: ModernMustardSeed/small-business-mcp-starter
Website: starter.modernmustardseed.com
Registry status: Active

Which apps can use it

Based on how this server connects and on each app’s own docs, checked Nov 10, 2026.

Connect over the internet in

Claude ChatGPT Goose LM Studio Msty Studio Cherry Studio Cursor VS Code + GitHub Copilot Visual Studio Windsurf (Devin Desktop)Zed Kiro Cline Continue JetBrains AI Assistant Claude Code Codex CLI Gemini CLI OpenCode nodecode Warp LibreChat Open WebUI Raycast

All apps, with pros and cons →

What it can do

Tool names and descriptions exactly as the server reported them on Nov 8, 2026. The maker wrote them, not us; we show them as plain text.

list_federal_holidays
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
next_federal_holidays
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.
check_business_day
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.
add_business_days
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 i
count_business_days
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.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 12, 2026

✓ Pass
Maker matches the repo
The registry name was verified against the domain modernmustardseed.com (the registry checks domain ownership)
✓ Pass
Still maintained
Code last changed 13 days ago
✓ Pass
Has a licence
Uses MIT
✓ Pass
Endpoint responds
Responded in 295 ms (HTTP 200)
– Not applicable
Sign-in with OAuth
No sign-in needed
✓ Pass
No hidden instructions in tool descriptions
Read 5 tool descriptions and found no hidden instructions to the AI

Discussion

Ask, share a tip or report that it does not work. Sorted by what people marked helpful.

No posts yet. Be the first to ask or share.

Posts here are written by users, not the PopNx team.

User reviews

No reviews yet

Compared with others in Docs, sheets & office worki

More stars than 0% of the other 3780 servers in this category
Published to the registry more recently than 49% of the other 3780 servers in this category
Basic checks equal to or better than 100% of the other 3780 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is Holiday Calendar safe?

It passed 5 of 5 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.

Is it still maintained?

The GitHub repo last changed 13 days ago, and the latest version (1.0.1) reached the registry 31 days ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT Business and above.

What can I use instead?

In the same category: Puter MCP, XcodeBuildMCP, XcodeBuildMCP

Others in the same category

Servers in the same category from other makers, sorted by stars.

Reading a card:↓ Downloads per weeki★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

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XcodeBuildMCP

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by cameroncookeWidely used↓ 130.5K/wk shared package★ 6.6KUpdated 14 months ago

Runs on your computer

Install

README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

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.

2. Run it and prove it works. (2 minutes)

pnpm dev

In a second terminal:

pnpm test

pnpm evals http://localhost:3000

You should see 32 pass from the unit tests and 35 of 35 passed from the evals. Open http://localhost:3000/docs/holidays to see the docs page reviewers read.

3. Make it yours. (2 minutes)

Edit lib/site.ts: company name, location, website, support inbox, security inbox, and the policy date. Every public page and security.txt read from it. Replace app/icon.svg and app/apple-icon.png with your own mark; the directory listing asks for an icon.

4. Deploy. (3 minutes)

Import the repository at vercel.com/new, or from the terminal:

vercel deploy --prod

Vercel sets VERCEL_PROJECT_PRODUCTION_URL, which the pages use for their links. Leave Attack Challenge Mode and any bot-protection rule off for your MCP paths: they answer Claude with a challenge page.

5. Check the deployment. (1 minute)

pnpm preflight https://your-project.vercel.app

pnpm evals https://your-project.vercel.app npx @modelcontextprotocol/inspector --cli https://your-project.vercel.app/holidays --transport http --method tools/list

Preflight checks HTTPS, no redirect, no 403 or 429, every public page returning 200, the MCP handshake and the annotation rules.

6. Try it in Claude. (1 minute)

In Claude, open Customize > Connectors > Add custom connector and paste https://your-project.vercel.app/holidays. Ask: "An invoice dated 2026-11-20 is due in 10 business days. What date is that?" In Claude Code:

claude mcp add --transport http holidays https://your-project.vercel.app/holidays

Build your own connector

Copy lib/holidays/tools.ts to lib/ /tools.ts. Declare each tool as a ToolSpec: name, title, description, zod input schema, annotations, a per-minute limit, optional global limits, the fields that are safe to log, and a run function that returns ok(data) or fail(code, sentence).
Copy app/holidays/route.ts to app/ /route.ts and point it at your tools.
Copy app/docs/holidays/page.tsx to app/docs/ /page.tsx. Keep the "For reviewers" section: you paste it into the form.
Rewrite app/privacy/page.tsx so every sentence is true of your tools: what they receive, what they read, what you keep and for how long, who else touches it.
Copy eval/holidays.eval.mjs. Write 20 to 50 cases from prompts real users type, with expected values from an authority outside your code. Include the error cases.
If a tool fetches a URL a user gave you, use safeFetch from lib/mcp/safe-fetch.ts. Never fetch a user-supplied URL directly.
Deploy, run pnpm preflight and pnpm evals against production, test every tool in Claude, then work through docs/SUBMISSION-CHECKLIST.md.

Why each pattern exists, with the rule it answers: docs/PATTERNS.md.

What is in the box

Path	What it does
`app/holidays/route.ts`	The connector endpoint. One file per connector.
`lib/mcp/tool.ts`	`ToolSpec`, `registerTools`, `runTool`: conventions, limits, errors, size cap, logging.
`lib/mcp/limits.ts`	Per-instance and global limits, never by IP; Redis with an in-memory fallback; a small cache.
`lib/mcp/safe-fetch.ts`	SSRF-safe fetch: public addresses only, guarded DNS lookup, five checked redirects, byte cap, deadline.
`lib/holidays/`	The example connector: the holiday engine and its five tools.
`lib/site.ts`	Company, support and security contacts, policy date. Edit first.
`app/docs`, `app/privacy`, `app/terms`, `app/support`	The pages reviewers and users open.
`app/.well-known/security.txt`	RFC 9116 security contact.
`eval/`	Dependency-free MCP client and the example's 35 checks against a live URL.
`scripts/preflight.mjs`	Pre-submission checks against a deployed URL.
`scripts/check-prose.mjs`	Fails on em and en dashes in tracked files.
`test/`	Unit tests for conventions, limits, SSRF guard and the example engine.
`docs/`	The submission checklist and the pattern notes.

Environment

The example runs with no environment variables. Optional:

Variable	Purpose
`SITE_URL`	Public origin, if you are not on Vercel or want a custom domain in page links.
`UPSTASH_REDIS_REST_URL`, `UPSTASH_REDIS_REST_TOKEN`	Global rate limits and cache shared across instances. The Vercel Marketplace integration sets `KV_REST_API_URL` and `KV_REST_API_TOKEN` instead; both are read. Without Redis, each instance limits itself in memory at one tenth of the global numbers.

Commands

Command	What it does
`pnpm dev`	Local server on port 3000.
`pnpm test`	Unit tests (Node's built-in runner).
`pnpm evals`	The example's evals against a running server.
`pnpm preflight`	Pre-submission checks against a deployed URL.
`pnpm typecheck`, `pnpm lint`, `pnpm build`	The usual.
`pnpm check:prose`	No em or en dashes in tracked files.

About the example

The Holiday Calendar computes the eleven U.S. federal holidays from 5 U.S.C. 6103, a public-domain statute, with the observance rule federal offices follow: Saturday holidays move to the Friday before, Sunday holidays to the Monday after. It covers 2021 through 2100. Its tools list a year of holidays, find the next ones, check whether a date is a business day, add business days to a date, and count business days in a span. It makes no network calls and stores nothing. The evals check its answers against the Office of Personnel Management's published schedules.

Contributing and security

Issues and pull requests are welcome; see CONTRIBUTING.md. Report vulnerabilities privately as described in SECURITY.md.

This kit is not affiliated with or endorsed by Anthropic. "Claude" is a trademark of Anthropic, PBC. Directory rules change; the checklist links every rule to Anthropic's documentation so you can confirm it before you submit.

Built by Modern Mustard Seed

This kit comes from Modern Mustard Seed, an AI studio in Kalispell, Montana that builds websites, AI voice agents and custom software for small businesses, managed for you, end to end.

Holiday Calendar

What it does

Install

Open Claude’s Connectors page

Click “+ Add” → “Add custom connector” and fill in these 2 fields

Turn it on in a chat

Try it

Open ChatGPT’s add-MCP page on the web

Fill in the name and address

Pick Holiday Calendar in a chat

Try it

Open Terminal

Paste this command and press Enter

Type /mcp in Claude Code

Try it

Click this button to open Cursor

Open the AI chat in Cursor in Agent mode

Try it

Click this button to open VS Code

Open the AI chat in VS Code in Agent mode

Try it

Over the web

At a glance

Which apps can use it

Related guides

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Discussion

User reviews

Compared with others in Docs, sheets & office worki

Common questions

Others in the same category

Puter MCP

XcodeBuildMCP

XcodeBuildMCP

README from the maker

Small Business MCP Starter Kit by Modern Mustard Seed

Working demo

Quickstart: 10 minutes

Build your own connector

What is in the box

Environment

Commands

About the example

Contributing and security

Built by Modern Mustard Seed

License