France Data MCP

French public registries as tools for AI agents: company records, property sale prices, housing energy performance, and short-term rental rates.

Endpoint: https://france-data-mcp.fly.dev/mcp (streamable HTTP)

Why this exists

The three REST APIs behind it are listed on API marketplaces, where they compete with 98,000 others for search placement. MCP is a different channel with different economics and much less crowding: Apify returns 80% of revenue to developers, MCPize 85%, against RapidAPI's 75%. More importantly, a listing that does not rank on one marketplace earns nothing there — a second channel decorrelates that risk.

This server owns no data. It is distribution.

Tools

Tool	Answers
search_companies	Find a French company by name, trade name or address
lookup_company	One company by SIREN, or the owner of a SIRET
validate_company_id	Is this SIREN/SIRET well-formed, and does it exist
property_prices	Median and percentile €/m² for a commune
property_price_trend	Did this local market rise or fall, year by year
energy_profile	Energy label distribution, and the share barred from letting
prices_by_energy_label	What an energy rating is worth locally
short_let_market	Nightly price percentiles for any city worldwide

Design notes

Docstrings are the interface. The model reads them to choose a tool and its arguments, so they say what a tool answers and when to prefer it — not how it works.

Responses are trimmed, not proxied. An LLM pays for every token it reads. Returning the full REST payload would make each call expensive and slow to reason over, so each tool returns the answer rather than the record.

Caveats pass through unchanged. Several of these statistics are easy to misread — most sharply, poorly rated homes selling at a premium in old city centres. An agent reporting a median should be able to report its limits too, so the caveat text travels with the number.

Access control

MCP_ACCESS_TOKEN unset leaves the server open, which is the right setting while the goal is directory listing and discovery. Set it to require a bearer token when selling access directly. Marketplaces handle their own billing, so a server distributed there runs open and lets the marketplace gate it.

Configuration

Variable	Purpose
COMPANY_API_SECRET / PROPERTY_API_SECRET / AIRBNB_API_SECRET	Proxy secrets for the three backends
PUBLIC_HOST	Hostname allowed past DNS-rebinding protection
MCP_ACCESS_TOKEN	Optional bearer token

The SDK rejects unknown Host headers to block DNS rebinding and allows only localhost by default. Without PUBLIC_HOST declared, every real request answers 421 Misdirected Request — which is exactly what happened on first deploy.

Running locally

pip install -r requirements.txt
uvicorn app.main:app --port 8080

Deploying

flyctl deploy --remote-only

Scale-to-zero, one machine.