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jp.bestcalendar/koyomi in the official MCP registry. Endpoint https://bestcalendar.jp/mcp.

The registry describes it as: Japanese calendar data (rokuyo, lucky days, solar terms, holidays, moon, sunrise), 1926-2080.

Connect it

The endpoint answers MCP over HTTP; that is how we read it. Add it to your client:

claude mcp add --transport http koyomi https://bestcalendar.jp/mcp

{
  "mcpServers": {
    "koyomi": {
      "url": "https://bestcalendar.jp/mcp"
    }
  }
}

code --add-mcp '{"name":"koyomi","type":"http","url":"https://bestcalendar.jp/mcp"}'

Some servers ask you to sign in the first time a client connects, or want a key from the people who run them; the server's own docs say which.

Let Claude Code check servers as it adds them

With the free lazaretto-guard plugin installed, when Claude Code adds a server for you or writes one into an MCP config, the plugin reads the server's tools first and asks you if one of our rules matches. Install it, restart Claude Code, then ask it to run the command above.

claude plugin marketplace add jamesdfinance-dev/lazaretto-plugins
claude plugin install lazaretto-guard@lazaretto-plugins

Tools it advertises

get_koyomi_day search_lucky_days convert_wareki_eto get_sun_moon_times list_holidays get_solar_term_times get_moon_phases get_koyomi_entity get_moon_events get_rokuyo_hours get_old_time count_days add_days check_business_day find_dates answer

Tool changes

We compare every full read of this server with the one before. No change in what its tools say has been seen since we started keeping this record on 2026-10-30.

Fingerprint of its tools at our last full read (2026-10-31): 6e712dfd11375305. A client can hash the tools it is served the same way and compare; the full value and a hash per tool are in this page as JSON.

Run this server? Show the check in your README

The badge reflects the latest weekly read:

[![MCP tool check](https://lazaretto.dev/mcp-registry/jp-bestcalendar-koyomi/badge.svg)](https://lazaretto.dev/mcp-registry/jp-bestcalendar-koyomi)

How this was checked

Lazaretto connects to the endpoint the way any MCP client does, asks the server to introduce itself and list its tools, and reads every name, description, parameter schema and server instruction for tool poisoning: hidden directive blocks, orders to read local secrets, parameters built to carry secrets or the conversation out, orders that redirect another server's tools, and invisible characters. It never calls a tool. What we found across the registry.

To run the same check every time Claude Code adds a server, install the free lazaretto-guard plugin. Browse every server in the index.

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