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

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:

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)

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

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

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

Licence

Apache-2.0. © Matematic Solutions / Wieslaw Mazur.