Geojp

io.github.55tarkunPublished by GitHub account 55tarkunv0.1.0Updated Oct 24, 2026

MCP server for Japan geodata: cadastral lot numbers (chiban) and reverse geocoding, for AI agents.

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Overview

AI-generated overview

Geojp exposes Japan-specific geodata APIs to AI assistants: cadastral lot numbers (chiban) and Japanese address geocoding from coordinates or addresses.

What you can do
Look up the cadastral parcel (chiban, ōaza/aza, municipality, survey precision) containing a latitude/longitude point via get_parcel. Reverse geocode coordinates to the nearest Japanese residential address, including prefecture, municipality, district and postal code. Forward geocode a partial address into up to 10 candidate locations. Retrieve address and chiban together in one parallel call with lookup_location, falling back to address-only when the point is outside chiban coverage.
When to use it
Useful for Japanese real estate due diligence, land transaction workflows, or any task that needs the cadastral lot number behind a coordinate, which general-purpose geocoders usually do not provide. Also handy when an assistant needs to convert between Japanese addresses and coordinates.
Requirements
Either connect to the hosted remote endpoint or run the npm package geojp-mcp locally with Node.js via npx. An API key from ReverseGeoJP/ChibanJP is required, supplied as the GEOJP_API_KEY environment variable for local use or as an Authorization bearer token for the remote endpoint. Network access to the upstream APIs is needed.
Before you install
The API key (GEOJP_API_KEY or the Authorization bearer token) is a secret and should not be shared or committed. Every call is proxied to the third-party ReverseGeoJP/ChibanJP production APIs, so coordinates and addresses are sent to that provider. Usage may be subject to that provider's terms or quotas.

Installation

In SourceWeft

  1. Open Geojp in the dashboard and add it to a workspace.
  2. Connect Authorization token credentials. They are stored privately and never shown on public pages.
  3. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/io.github.55tarkun%2Fgeojp/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "geojp": {
      "type": "http",
      "url": "https://mcp.reversegeojp.com/",
      "headers": {
        "Authorization": "Bearer <YOUR_TOKEN>"
      }
    }
  }
}

README

geojp-mcp

日本語版 README はこちら

An MCP (Model Context Protocol) server that exposes two Japan-specific geodata APIs as tools for AI agents (Claude Code, Claude Desktop, and other MCP clients):

  • ChibanJP — coordinates → chiban (地番, the official cadastral lot number recorded at Japan's Legal Affairs Bureau). Chiban rarely maps predictably to a residential address (住居表示) and is not exposed by most general-purpose geocoders.
  • ReverseGeoJP — coordinates ⇄ Japanese address (reverse geocoding / forward geocoding).

Why chiban?

Japan uses two independent addressing systems: the residential address (住居表示) that appears on maps and mail, and the chiban — the cadastral lot number used in property registries, land transactions, and legal documents. The two do not follow a predictable pattern, so converting between them requires a dedicated lookup against registry map data, not a lookup table.

Chiban matters for real estate due diligence, land transaction platforms, and any workflow that touches Japan's registry system — a growing need as foreign investment in Japanese real estate rises. Most global geocoding APIs do not source chiban directly from registry map data, which is why this exists as a standalone tool.

Tools

ToolBacking APIInputReturns
get_parcelChibanJP /parcellat, lonChiban (cadastral lot number), ōaza/aza, municipality, and survey precision class for the containing parcel
reverse_geocodeReverseGeoJP /reverselat, lonNearest residential address (prefecture, municipality, district, postal code)
geocodeReverseGeoJP /geocodeaddressUp to 10 candidate locations for a partial address match
lookup_locationBoth, in parallellat, lonAddress and chiban together in one call (an orchestration example — succeeds with address-only if the point falls outside ChibanJP's current coverage)

All tools share a single API key. Get one at reversegeojp.com.

Two ways to run it

The tool definitions live in src/tools.ts and are shared by both entry points:

  • Local (stdio) — src/index.ts. Your MCP client launches it as a child process on your machine. One user, one API key.
  • Remote (HTTP, Cloudflare Workers) — src/worker.ts. Already deployed at https://mcp.reversegeojp.com; anyone can connect with their own API key, no build step required.

Setup (local/stdio)

bash
npm install -g geojp-mcp

or, from source:

bash
npm installnpm run build

The server reads the API key from the GEOJP_API_KEY environment variable. You normally don't run it directly — your MCP client starts it as a subprocess (see below).

Register with Claude Code

bash
claude mcp add --scope user geojp -e GEOJP_API_KEY=your-api-key-here -- npx geojp-mcp

--scope user makes it available across all projects on your machine (omit it to register for the current project only). Verify with claude mcp list.

Argument order matters: -e/--env accepts multiple values, so it will swallow subsequent arguments if placed before the server name. Keep the order: add, then the server name, then -e.

Or configure manually in .mcp.json / ~/.claude.json:

json
{  "mcpServers": {    "geojp": {      "type": "stdio",      "command": "npx",      "args": ["geojp-mcp"],      "env": {        "GEOJP_API_KEY": "your-api-key-here"      }    }  }}

Register with Claude Desktop

Add the same block to the mcpServers section of claude_desktop_config.json, then restart Claude Desktop. Four tools (reverse_geocode, geocode, get_parcel, lookup_location) become available.

Setup (remote/HTTP)

Connect directly to the hosted server with your own API key — no install or build required:

bash
claude mcp add --scope user --transport http geojp-remote https://mcp.reversegeojp.com --header "Authorization: Bearer your-api-key-here"

Health check: GET https://mcp.reversegeojp.com/health.

Remote server design notes

  • No bindings, stateless: the Worker holds no session state and uses no Durable Objects. Every call reads the API key from the Authorization header and proxies straight through to the ReverseGeoJP/ChibanJP production APIs. This avoids the paid Workers plan that Durable Objects require, so it runs on the same free plan as reverse-geo-jp/chibanjp with no added infrastructure cost (the more common McpAgent pattern from agents-sdk assumes Durable Objects and a paid plan).
  • Web Standards transport: uses @modelcontextprotocol/sdk's WebStandardStreamableHTTPServerTransport, since the Node-only StreamableHTTPServerTransport depends on http.IncomingMessage/ServerResponse, which don't exist in the Workers runtime.
  • Gotcha: reversegeojp-client/chibanjp-client default to holding a bare, unbound fetch (this.fetchImpl = options.fetch ?? fetch), which throws "Illegal invocation" on Cloudflare Workers. Fixed by passing an explicitly-bound fetch into the client constructor options in createGeojpMcpServer() (see boundFetch in src/tools.ts). Also fixed upstream in geojp-api-clients v0.1.1 (fetch.bind(globalThis)); geojp-mcp depends on that version, and keeps the local boundFetch as a harmless fallback.

Deploy / local dev

bash
npm run worker:dev     # local wrangler dev server (http://127.0.0.1:8787 etc.)npm run worker:check   # typecheck against the Workers tsconfig onlynpm run worker:deploy  # deploy to production

Smoke test (no API key required — wiring check only)

bash
npm run smoke-test

Starts the server with a dummy key and confirms the tool list loads and a real API call correctly returns an invalid_api_key error.

Why this exists

ReverseGeoJP/ChibanJP were already running as APIs meant to be called directly by developers reading the docs. This project exposes them as MCP tools so AI agents can discover and call them automatically — reusing the existing production infrastructure while building hands-on MCP/agent-integration experience.

License

MIT

Source: README.md at commit a9ee994

Tools

0
This server asks for a credential such as an API key, so SourceWeft could not read its tools without one and has not indexed them.

Version history

1
  1. v0.1.0LatestSep 16, 2026

Score

85% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listed15 pts

    Answer tools/list without a credential, or ship a package that starts in a sandbox without one.

  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts