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Japan Business Tools
jp.ossalt/jp-biz-tools in the official MCP registry.
Endpoint https://biz.ossalt.jp/mcp.
The registry describes it as: Japanese holidays, business days, eras, postal codes, addresses and corporate numbers.
We read its 13 tools on 2026-10-27. Nothing in them matched our tool-poisoning rules. It also sets server instructions, text a client puts in front of the model on connect; those were read too.
A clean read means these rules found nothing, not that the server is harmless. A server can change its tools at any time, which is why the index reads it again every week.
Tools it advertises
list_holidays check_business_day add_business_days count_business_days adjust_to_business_day last_business_day_of_month to_japanese_era from_japanese_era lookup_postal_code search_postal_code normalize_address lookup_corporate_number search_corporation_by_name
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[](https://lazaretto.dev/mcp-registry/jp-ossalt-jp-biz-tools)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.