Houan MCP

@codeagentjp/houan-mcp

Local stdio MCP server for searching Japanese Diet bills (衆参議案情報) and committee Q&A records via the NDL Kokkai (国会会議録検索システム) API.

This server does not call an LLM. It only returns source-backed Diet data, with primary URLs (NDL Kokkai, 衆議院議案情報, 参議院議案情報) so your MCP client (Claude Desktop, Claude Code, Cursor, or any other agent) can cite the original source.

Sister package: @codeagentjp/egov-law-mcp for current Japanese laws (e-Gov Law Search). houan-mcp covers the *legislative process* side: bills under deliberation, committee questionings, and full meeting transcripts.

Status

MVP. Four tools:

• find_diet_qa — full-text search across all Diet committee speeches via the NDL Kokkai API. Filter by date, chamber, committee, speaker.
• get_meeting_record — retrieve a single committee's full transcript by issueID.
• search_bills — search current-session bills in either house by title keyword.
• get_bill — retrieve detail of one bill (proceedings timeline, committee assignment, full-text URL).

Requirements

• Node.js 20 or later
• Network access to https://kokkai.ndl.go.jp, https://www.shugiin.go.jp, https://www.sangiin.go.jp

Install

From npm:

{

"mcpServers": { "houan": { "command": "npx", "args": ["-y", "@codeagentjp/houan-mcp"] } } }

From source:

git clone https://github.com/SHAYOUWORLD/houan-mcp.git

cd houan-mcp node bin/houan-mcp.mjs

{

"mcpServers": { "houan": { "command": "node", "args": ["/absolute/path/to/houan-mcp/bin/houan-mcp.mjs"] } } }

Tools

find_diet_qa

Full-text search of Diet committee speeches via the NDL Kokkai API.

{

"keyword": "クロード ミトス", "from": "2026-04-01", "until": "2026-04-25", "chamber": "衆議院", "committee": "外務委員会", "limit": 5 }

Returns matched speeches with speaker, position, committee context, and direct NDL URL.

get_meeting_record

Retrieve a single full transcript by issueID.

{

"issueID": "122103968X00620260410" }

search_bills

Search 衆議院議案情報 / 参議院議案情報 by title keyword.

{

"keyword": "情報", "chamber": "both", "session": 222, "limit": 20 }

When session is omitted, the server reads the session list behind the 衆議院議案情報 dropdown (.../html/gian/pulldown.htm, one small request, cached for 5 minutes like other responses) and searches the highest session listed, for both chambers. If that list cannot be read, it searches 222 (checked 2026-10-28) and adds an entry to warnings. query.sessionSource is latest, fallback, or argument. Specify session explicitly for historical sessions; no session list is fetched then.

For Shugiin results, session is the searched session, submittedSession is the session in which the item was introduced, and billType distinguishes 衆法 / 参法 / 閣法 and other agenda items. billNumber is the official number (or null for unnumbered items); status comes from 審議状況. Unpublished proceedings/full-text links are null.

HTTP, network, timeout, and unrecognized Shugiin table errors are returned as an MCP tool result with isError: true. Its text contains error, sourceErrors (chamber, URL, message) and warnings, rather than a successful zero-hit result. When searching both, a failure in either chamber fails the whole search; request one chamber explicitly if you want to retry it alone. A successful search with no title matches still returns matched: 0 and results: [].

get_bill

Retrieve a bill detail page (proceedings timeline, committee assignment, full-text URL). The proceedingURL must be a URL returned by search_bills — it is validated against the chamber's allowed path prefix before fetching.

{

"chamber": "shugiin", "proceedingURL": "https://www.shugiin.go.jp/internet/itdb_gian.nsf/html/gian/keika/1DE..." }

Data Sources and Attribution

This package uses three Japanese public sources:

• NDL Kokkai (国会会議録検索システム) — https://kokkai.ndl.go.jp/ · API documentation. Diet records published 1947–. No auth required. The API terms ask machine clients not to send concurrent requests and to wait a few seconds between requests; this server enforces that (see Request pacing).
• 衆議院議案情報 — https://www.shugiin.go.jp/internet/itdb_gian.nsf/html/gian/menu.htm
• 参議院議案情報 — https://www.sangiin.go.jp/japanese/joho1/kousei/gian/current/gian.htm

Tool results include the source URL. When you publish or redistribute output based on this package, include an appropriate attribution. Suggested:

出典: 国会会議録検索システム (https://kokkai.ndl.go.jp/) / 衆議院議案情報 / 参議院議案情報

Request pacing

The NDL Kokkai API terms (section 4) ask machine clients to avoid concurrent requests and to wait a few seconds after each response before sending the next one. find_diet_qa and get_meeting_record therefore:

• send at most one request to kokkai.ndl.go.jp at a time, even when a client calls several tools at once or sends a JSON-RPC batch;
• start each request at least 3 seconds after the previous one finished. Set HOUAN_MCP_NDL_INTERVAL_MS to wait longer; values below 3000 are ignored.

Identical queries within 5 minutes are answered from an in-process cache and do not reach NDL. Several NDL calls in a row take about 3 seconds each. The pacing applies within one server process; if you run several copies, keep their combined traffic within the same terms.

HOUAN_MCP_TIMEOUT_MS (default 20000) sets the per-request timeout. It starts when the request is sent, not while it waits for its turn.

Example: pulling a Mythos Q&A

The 4/10 2026 衆議院外務委員会 questioning by 宇佐美登 (チームみらい) on Anthropic's Claude Mythos Preview can be retrieved like this:

{

"tool": "find_diet_qa", "arguments": { "keyword": "クロード", "from": "2026-04-01", "until": "2026-04-30" } }

The response includes 花田貴裕 政府参考人's verbatim answer with meetingURL pointing to the canonical NDL record at https://kokkai.ndl.go.jp/txt/122103968X00620260410.

Safety Notes

• This package is a legislative reference tool, not legal/political advice.
• It does not execute shell commands.
• It writes JSON-RPC messages only to stdout and logs only to stderr.
• It fetches only the NDL Kokkai API and 衆/参 議案情報 endpoints.
• Diet records in NDL typically appear with a 1–2 week lag after the committee meeting. If a recent meeting cannot be found, check back later or consult the chamber's video library directly.

Development checks

npm test

Tests launch the stdio server with network requests replaced by local official-HTML samples. They cover Shugiin search/proceedings, failure reporting, and the existing Sangiin and NDL tools. Sample sources and capture details are in test/fixtures/README.md.

Related

• Sibling MCP for current laws: @codeagentjp/egov-law-mcp
• Roadmap (法令diff / 自治体条例 / 判例 MCPs): SHAYOUWORLD/egov-law-mcp#1
• Use cases (Japanese): houan-mcp の7つの実用ユースケース (codeagent.jp)
• From bills to current law (Japanese): houan-mcpとe-Gov法令MCPの調査フロー (codeagent.jp)
• Other Japanese public-data APIs and MCP servers: codeagent.jp/guides/public-data-api/

License

MIT © codeagent.jp