# QuantaFlow x402 API Gateway — Frankfurter Proxy

> QuantaFlow x402 API Gateway — Frankfurter Proxy is a paid API for AI agents from quanta-roan.vercel.app, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-12).

Proxies requests to the Frankfurter currency exchange rate API via the x402 micropayment protocol, charging $0.01 USDC per call.

## Facts

- Endpoint: POST https://quanta-roan.vercel.app/api/service/frankfurter?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/quantaflow-x402-api-gateway-frankfurter-proxy-57235e8b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_MFPU6Ic-xI7OFRtcvW1RV

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 quantaflow-x402-api-gateway-frankfurter-proxy-57235e8b -d '<json body>'
```

Example prompt: What's the current EUR to USD exchange rate? Use the Frankfurter proxy and charge my wallet the $0.01 USDC fee.

## When to prefer this

Choose this endpoint when you need Frankfurter ECB exchange rate data and are operating in a web3/x402 micropayment context where per-call USDC billing is acceptable. It is ideal for agents that already have an x402-capable wallet and want to avoid API key management for currency data. Prefer direct Frankfurter API access if you need higher volume without per-call fees.

## Known failure modes

- Payment failure — insufficient USDC balance causes 402 Payment Required with no upstream call made
- Invalid path — malformed or unsupported Frankfurter path returns upstream 404 or 400 error
- Upstream unavailability — Frankfurter service down returns a gateway error
- Invalid query parameters — unsupported currency codes or date formats return Frankfurter validation errors
- Network timeout — slow upstream response may cause gateway timeout

## How this service works

Every request, a quantum of value. x402 protocol-based payment endpoint for web3/DeFi tools.

## Output

The raw upstream Frankfurter API response body (JSON) containing exchange rate data, currency lists, or historical rate data, along with the content type header — passed through as-is after the x402 micropayment is settled.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "body": {
   "type": "string",
   "description": "Optional JSON body forwarded to POST requests."
  },
  "path": {
   "type": "string",
   "description": "Path below the selected upstream origin."
  },
  "query": {
   "type": "object"
  },
  "method": {
   "enum": [
    "GET",
    "POST"
   ],
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "description": "The upstream response body and content type are passed through after successful payment."
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/quantaflow-x402-api-gateway-frankfurter-proxy-57235e8b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from quanta-roan.vercel.app](https://www.zero.xyz/host/quanta-roan.vercel.app/llms.txt)