# French Undervalued Property Finder (Biens Sous-Cotés)

> French Undervalued Property Finder (Biens Sous-Cotés) is a paid API for AI agents from api.x-402.online, paid per call via x402, $0.05/call, status unknown (last checked 2026-10-23).

Finds French real estate listings priced below the median price per square metre of nearby actual DVF sales transactions, returning the discount gap as a percentage.

## Facts

- Endpoint: POST https://api.x-402.online/v1/fr/biens-sous-cotes?utm_source=zero.xyz
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-23
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/french-undervalued-property-finder-biens-sous-cot-s-845d4122
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_yauvSZ_leIiRp1l5w6ZAO

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability french-undervalued-property-finder-biens-sous-cot-s-845d4122 -d '<json body>'
```

Example prompt: Can you find me undervalued properties for sale in Lyon — specifically listings where the asking price is below what similar properties have actually sold for nearby, and show me how big the discount is?

## When to prefer this

Choose this endpoint when you need to cross-reference live French property listings against actual completed transaction data (DVF) rather than other asking prices. It is specifically useful for identifying genuine market discounts in France, for investment screening, or for buyers who want to avoid overpaying. Prefer this over generic property search APIs when the core need is value analysis grounded in real sold-price data rather than listing-to-listing comparison.

## Known failure modes

- Area with insufficient DVF transaction data returns no results or unreliable median
- Overly broad or ambiguous geographic query may return unexpected or empty results
- DVF data lag means very recent market shifts may not be reflected in the median
- Payment failure (x402 micropayment not processed) results in 402 response and no data
- Invalid or missing required query parameters return a 400 error

## How this service works

Pay-per-call APIs for AI agents — x402 protocol, USDC on Base, no account needed.

## Output

Returns a list of French property listings in the specified area whose asking price is below the median price per square metre derived from DVF (Demandes de Valeurs Foncières) actual sale transactions nearby. Each listing includes the asking price, the reference median price per sqm from real transactions, and the undervaluation gap expressed as a percentage discount.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {}
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "candidates": [
   {
    "url": "https://...",
    "type": "Appartement",
    "price": 243000,
    "gapPct": -31,
    "surface": 70,
    "pricePerM2": 3307
   }
  ],
  "candidatesCount": 6,
  "soldMedianPerM2": 4778
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/french-undervalued-property-finder-biens-sous-cot-s-845d4122/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.x-402.online](https://www.zero.xyz/host/api.x-402.online/llms.txt)