DVF Paris — MCP App

An interactive MCP App that displays Paris real estate prices per arrondissement, directly inside Claude.

Built with the MCP Apps SDK (@modelcontextprotocol/ext-apps).

What it does

Ask Claude about Paris real estate prices and get an interactive widget with:

• Fullscreen mode (v0.8): split layout with map (60%) and info panel (40%), interactive search
• Interactive map (Leaflet + OpenStreetMap) highlighting the arrondissement
• Choropleth sections (v0.6): cadastral sections colored by median price, clickable for details
• Price stats: average price/m², median price/m², number of sales
• Apartments / Houses toggle
• Comparison mode: compare two arrondissements side-by-side with a bar chart
• Address search (v0.5): search by address and get stats for the cadastral section
• UI-driven search (v0.8): search addresses and browse arrondissements directly from the widget

Data source: DVF (Demandes de Valeurs Foncieres) from data.gouv.fr.

Architecture

Claude                    MCP Server               UI (iframe)
  │                          │                         │
  │── "prix Paris 11" ──────>│                         │
  │                          │── get-dvf-stats ───────>│
  │                          │   structuredContent     │── Map + Stats
  │                          │                         │
  │── "compare 6e vs 11e" ──>│                         │
  │                          │── compare-dvf-stats ───>│
  │                          │   mode: "compare"       │── Map + Bar chart
  │                          │                         │
  │── "prix rue Roquette" ──>│                         │
  │                          │── search-dvf-address ──>│
  │                          │   mode: "address"       │── Map + Marker + Compare

1. Claude calls get-dvf-stats, compare-dvf-stats or search-dvf-address
2. The tool returns data + a reference to ui://dvf/mcp-app.html
3. Claude fetches the resource and displays it in a sandboxed iframe
4. The UI receives data via app.ontoolresult

MCP Tools

Tool	Input	Output
get-dvf-stats	arrondissement (1-20)	Price stats for one arrondissement
compare-dvf-stats	arrondissement_1, arrondissement_2 (1-20)	Side-by-side comparison with bar chart
search-dvf-address	adresse (string)	Stats for cadastral section + comparison with arrondissement

Stack

Component	Technology
MCP Apps SDK	@modelcontextprotocol/ext-apps
MCP Server	@modelcontextprotocol/sdk
Build	Vite + TypeScript
UI	Vanilla JS
Map	Leaflet + OpenStreetMap (no API key needed)
Charts	Pure SVG (no dependencies)
Transport	stdio (Claude Desktop) or Streamable HTTP

External APIs

API	Usage
MCP data.gouv	Real-time DVF stats
API Géoplateforme	Address geocoding
cadastre.data.gouv.fr	Cadastral section geometries (GeoJSON)

Setup

npm install
npm run build

Claude Desktop configuration

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "dvf-paris": {
      "command": "bash",
      "args": ["-c", "cd /path/to/dvf-mcp-app && npx tsx main.ts --stdio"]
    }
  }
}

Then restart Claude Desktop.

Development

# Watch mode (UI hot reload + server)
npm run dev

# Build only
npm run build

# Run server (Streamable HTTP on port 3001)
npm run serve

Project structure

dvf-mcp-app/
├── server.ts              # MCP Server + Tools + Resource
├── main.ts                # Entry point (stdio + HTTP)
├── mcp-app.html           # UI shell (HTML)
├── src/
│   ├── mcp-app.ts         # UI logic (map, chart, host communication)
│   ├── mcp-app.css        # Widget styles
│   ├── api/               # External API clients
│   │   ├── cadastre.ts    # Cadastre GeoJSON client
│   │   ├── data-gouv.ts   # MCP data.gouv client
│   │   └── geoplateforme.ts # Geocoding client
│   └── data/
│       ├── dvf-paris.json          # Pre-computed stats (fallback)
│       └── arrondissements.geojson.json  # GeoJSON boundaries
├── package.json
├── tsconfig.json
└── vite.config.ts

Roadmap

• [x] v0.1 — Basic stats widget
• [x] v0.2 — Interactive map with Leaflet
• [x] v0.3 — Comparison mode (2 arrondissements)
• [x] v0.4 — Real-time data via data.gouv.fr API (with JSON fallback)
• [x] v0.5 — Address search with cadastral section stats
• [x] v0.6 — Choropleth cadastral sections (clickable, color-coded by price)
• [ ] v0.7 — Link to recent transactions (optional)
• [x] v0.8 — Fullscreen mode with interactive search (split layout, callServerTool)

License

MIT