# Holiday Calendar (remote · starter.modernmustardseed.com)

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

- Trust score: 78/100 (medium)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-10-22

## Components

- remote · `starter.modernmustardseed.com`: 78/100 (this document), [markdown](https://verifymcp.io/servers/com-modernmustardseed-holiday-calendar/holidays.md), [page](https://verifymcp.io/servers/com-modernmustardseed-holiday-calendar/holidays)

## Channel facts

- Endpoint: `https://starter.modernmustardseed.com/holidays`
- Transports: `streamable-http`
- Auth: `none`
- Version: `1.0.1`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-10-22.

- **Endpoint Security**: 80/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - No authorisation is required to call this server. Every tool declares its destructiveHint and none is destructive, so open access doesn't expose one.
  - HTTPS is enforced; there's no plaintext access path.
  - The HSTS (Strict-Transport-Security) header is present.
  - DNSSEC check failed: this domain isn't protected by DNSSEC.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 76/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 741 tokens (~148/item across 5 items; 5 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 33/100
  - Stability observed for 10 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 5 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 6 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a current MCP spec version (2026-07-28).

## Install

### How do I install the Holiday Calendar MCP server?

Holiday Calendar is a hosted endpoint at https://starter.modernmustardseed.com/holidays, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

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

### Cursor

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

### VS Code

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

### Codex

```toml
[mcp_servers.com-modernmustardseed-holiday-calendar]
url = "https://starter.modernmustardseed.com/holidays"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "com-modernmustardseed-holiday-calendar": {
      "type": "remote",
      "url": "https://starter.modernmustardseed.com/holidays",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add com-modernmustardseed-holiday-calendar --url 'https://starter.modernmustardseed.com/holidays' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  com-modernmustardseed-holiday-calendar:
    url: "https://starter.modernmustardseed.com/holidays"
```

### Netclaw

```json
{
  "McpServers": {
    "com-modernmustardseed-holiday-calendar": {
      "Transport": "http",
      "Url": "https://starter.modernmustardseed.com/holidays"
    }
  }
}
```

### Vellum

```bash
assistant mcp add com-modernmustardseed-holiday-calendar -t streamable-http -u 'https://starter.modernmustardseed.com/holidays'
```

### Other

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

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-10-21 (score 78, +1)

No change was recorded against any check on this day. Stability & Change Management went from 27 to 30. That category is still filling its 30-day observation window: 8 days of observed history at the previous scan, 9 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-19 (score 77, +1)

No change was recorded against any check on this day. Stability & Change Management went from 20 to 23. That category is still filling its 30-day observation window: 6 days of observed history at the previous scan, 7 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-16 (score 76, +1)

No change was recorded against any check on this day. Stability & Change Management went from 10 to 13. That category is still filling its 30-day observation window: 3 days of observed history at the previous scan, 4 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-14 (score 75, +1)

No change was recorded against any check on this day. Stability & Change Management went from 3 to 7. That category is still filling its 30-day observation window: 1 days of observed history at the previous scan, 2 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-13 (score 74, 0)

- [functional improvement] Stability: unverified → 0.03

### 2026-10-12 (score 74)

First indexed and scored.

## MCP tools (5)

### `list_federal_holidays` (~115 tokens)

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 5 U.S.C. 6103. Use it to answer which days federal offices close in a year.

Input parameters:

- `year` (integer, required): Calendar year, 2021 through 2100.

### `next_federal_holidays` (~126 tokens)

Find the 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.

Input 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.

### `check_business_day` (~89 tokens)

Check a 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.

Input parameters:

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

### `add_business_days` (~176 tokens)

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 is a holiday. Returns the resulting date and every holiday it skipped. Up to 1,000 business days either way.

Input parameters:

- `business_days` (integer, required): 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.
- `start_date` (string, required): The date to count from. It is not counted itself, written YYYY-MM-DD (for example 2026-11-26). Covers 2021 through 2100.

### `count_business_days` (~152 tokens)

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.

Input parameters:

- `end_date` (string, required): 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.
- `start_date` (string, required): 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.

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/com-modernmustardseed-holiday-calendar/holidays#diagnostics

## Score history

- 2026-10-22: 78
- 2026-10-21: 78
- 2026-10-20: 77
- 2026-10-19: 77
- 2026-10-18: 76
- 2026-10-17: 76
- 2026-10-16: 76
- 2026-10-15: 75
- 2026-10-14: 75
- 2026-10-13: 74
- 2026-10-12: 74

## Common questions

### What is the Holiday Calendar MCP server?

Holiday Calendar is an MCP server listed in the public MCP registry as com.modernmustardseed/holiday-calendar. U.S. federal holidays with observed dates and business-day math. Example from an open-source kit. This page covers its hosted endpoint (https://starter.modernmustardseed.com/holidays).

### Is the Holiday Calendar MCP server safe to use?

Holiday Calendar scores 78 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the Holiday Calendar MCP server expose?

Holiday Calendar exposes 5 tools: list_federal_holidays, next_federal_holidays, check_business_day, add_business_days, count_business_days. Their descriptions and schemas cost roughly 658 tokens of context every time the server is loaded.

### Does the Holiday Calendar MCP server require authentication?

No. We connected to Holiday Calendar without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

### Is the Holiday Calendar MCP server still maintained?

Holiday Calendar is still listed as active in the MCP registry. We last reached this channel on 22 October 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

## Links

- Remote endpoint: https://starter.modernmustardseed.com/holidays
- Repository: https://github.com/ModernMustardSeed/small-business-mcp-starter
- Website: https://starter.modernmustardseed.com/docs/holidays
- Changelog RSS feed: https://verifymcp.io/servers/com-modernmustardseed-holiday-calendar/holidays.xml
- Changelog JSON feed: https://verifymcp.io/servers/com-modernmustardseed-holiday-calendar/holidays.json
- HTML version of this page: https://verifymcp.io/servers/com-modernmustardseed-holiday-calendar/holidays