# Cross-Store Price Intent

Give a product query, get offers from Google Shopping, Amazon, eBay and Walmart.

- endpoint: `GET https://marketplaceforaiagents.com/api/public/v1/cross-store-price`
- category: intents
- price: $0.005 USDC per call (5000 atomic, 6 decimals)
- free tier: 3 calls per agent identity, shared across all endpoints (unknown/generic clients draw from a site-wide 100 successful free calls per UTC day; crawlers get none)
- settlement: USDC on Base mainnet `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`, payee `0x05e82e03753c7bc99fb24d10a876cce53f24b7b7`, scheme `exact`
- sandbox: append `?network=base-sepolia` for testnet USDC + mock data
- results key: `results`
- html: https://marketplaceforaiagents.com/listings/cross-store-price

## What it returns

One product query priced across four retail surfaces in a single call: Google Shopping, Amazon, eBay and Walmart.

## Use cases

- Best-price selection for a purchasing agent
- Arbitrage scanning
- Retail price-spread analysis

## Parameters

| param | type | required | default | description |
| --- | --- | --- | --- | --- |
| `q` | string | yes | — | Product query sent to all four retail engines |
| `gl` | string | no | us | Country code for results |
| `hl` | string | no | en | Interface language code |

## Example call

```bash
curl -s "https://marketplaceforaiagents.com/api/public/v1/cross-store-price?q=example"
```

## Response shape

```json
{
  "intent": "cross-store-price",
  "chain": [
    "google-shopping",
    "amazon-search",
    "ebay-search",
    "walmart-search"
  ],
  "steps_run": 4,
  "results": {
    "google-shopping": {
      "note": "Normalized response of /api/public/v1/google-shopping"
    },
    "amazon-search": {
      "note": "Normalized response of /api/public/v1/amazon-search"
    },
    "ebay-search": {
      "note": "Normalized response of /api/public/v1/ebay-search"
    },
    "walmart-search": {
      "note": "Normalized response of /api/public/v1/walmart-search"
    }
  }
}
```

## Payment

1. Call without `X-PAYMENT`. The first 3 calls per identity (across all endpoints) return 200 with an `X-Free-Calls-Remaining` header.
2. After that the response is `402` with an `accepts[]` requirement.
3. Sign the EIP-3009 USDC authorization, base64 the x402 payload, resend as `X-PAYMENT`.
4. Settlement receipt returns in the `X-PAYMENT-RESPONSE` header.