jp-eli-mcp

An MCP server for Japan's official e-Gov law search API (laws.e-gov.go.jp), run by the Digital Agency. It searches, fetches, and cites national legislation - acts, cabinet orders, ministerial ordinances - with a verifiable citation on every response.

Part of the MateMatic eu-legal-mcp production line, extended into Asia. Same citation contract (a stable identifier + a human-readable citation + a source URL) as the 18 EU/EEA connectors, adapted for a jurisdiction with no ELI scheme.

Scope. Discovery is by law title (jp_search_laws) or full-text keyword (jp_search_by_keyword); fetch a specific article (jp_get_article) or the full text (jp_get_full_text, truncated for very large laws such as the Civil Code). Every response carries a dataset_note.

Licence. e-Gov law data is official public information published by the Japanese government as open data (keyless, REST/JSON). This connector relays it with attribution and a source_url.

The tools

Tool	What it does
`jp_search_laws`	Search laws by (partial) title.
`jp_search_by_keyword`	Full-text search across all laws, with highlighted snippets.
`jp_get_law`	Metadata for a law by `law_id`: title, law number, promulgation date.
`jp_get_article`	The text of one article of a law, by `law_id` and `article_num`.
`jp_get_full_text`	The full text of a law (truncated at ~300,000 characters).
`jp_coverage`	Declare what this connector covers, when each family was captured, and - explicitly - what it does NOT cover. Every gap carries a fallback.

Every response carries the contract: eli_uri (Japan has no ELI - this is the durable e-Gov viewer URL, e.g. https://laws.e-gov.go.jp/law/129AC0000000089, see eli_note), human_readable_citation (e.g. 民法（明治二十九年法律第八十九号）), and source_url (the machine-readable API URL).

Install

Not yet on PyPI - install from source until the first release ships:

bash

git clone https://github.com/matematicsolutions/jp-eli-mcp
cd jp-eli-mcp
pip install -e .

Once released, this will be uvx jp-eli-mcp.

Configuration via env:

JP_ELI_BASE_URL - default https://laws.e-gov.go.jp/api/2
JP_ELI_CACHE_DIR - default ~/.matematic/cache/jp-eli
JP_ELI_AUDIT_DIR - default ~/.matematic/audit

No API key. e-Gov's law search API is keyless.

Configure (Claude Code / any MCP client)

config.json

{
  "mcpServers": {
    "jp-eli-mcp": { "command": "jp-eli-mcp" }
  }
}

Windows 11 with Smart App Control

Smart App Control blocks unsigned executables, which covers uvx.exe, pip.exe and the jp-eli-mcp.exe launcher that pip writes at install time. The python.exe and py.exe from the python.org installer are signed by the Python Software Foundation, so running the module through the interpreter works:

bash

python -m pip install jp-eli-mcp
python -m jp_eli_mcp

pip.exe is blocked for the same reason, so install with python -m pip, not pip install. If python is not on PATH, use the Windows launcher: py -3 -m jp_eli_mcp.

config.json

{ "mcpServers": { "jp-eli-mcp": { "command": "python", "args": ["-m", "jp_eli_mcp"] } } }

Do not turn Smart App Control off to work around this - it cannot be re-enabled without reinstalling Windows.

Governance

Public data only - read-only against e-Gov; no client data leaves the machine.
Audit log - every tool call appends one JSON line to ~/.matematic/audit/jp-eli-mcp.jsonl.
Vendor-neutral - talks only to laws.e-gov.go.jp; no LLM provider, no telemetry.
Verifiable citations - every response is independently checkable via source_url.

See CONSTITUTION.md and DISCOVERY.md.

Tests

Terminal

pip install -e ".[dev]"
pytest tests/test_instructions_drift.py -v   # offline
pytest tests/test_smoke.py -v                # hits live e-Gov