# realx402-seller

> realx402-seller is a paid API for AI agents from goodsong.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Verifies an x402 seller endpoint by checking it responds with a valid 402 challenge, validates its schema consistency, and screens its payout address against sanctions oracles

## Facts

- Endpoint: POST https://goodsong.dev/verify/seller
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/realx402-seller-754e839e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_DXhk1teWhg43OrZb7yUbC

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 realx402-seller-754e839e -d '<json body>'
```

Example prompt: Before we pay that x402 seller at https://api.example.com/data using a POST request, can you run a verification check to make sure its 402 challenge is well-formed, its schema is internally consistent, and its payout address isn't sanctioned?

## When to prefer this

Choose this endpoint when an AI agent needs to perform pre-payment due diligence on an x402 seller, especially when integrating new or untrusted x402 APIs into an automated payment pipeline. It is the right tool when you need both protocol-level validation (well-formed 402 challenge, schema consistency) and compliance screening (sanctions check on payout address) in a single call. Prefer it over manual inspection or generic URL checkers when the seller uses the x402 payment protocol on Base.

## Known failure modes

- Seller URL does not exist or is unreachable — verification fails with connectivity error
- Seller returns a non-402 response — challenge validity check fails
- Payout address is not a Base network address — sanctions check may be skipped or limited
- Schema inconsistency detected — reported but not necessarily blocking
- Chainalysis or Blockscout oracle temporarily unavailable — sanctions check may be inconclusive
- Malformed or missing input parameters — returns validation error

## How this service works

Verify an x402 seller before paying it: does it exist and respond with a well-formed 402 challenge, is its own declared input/output schema internally consistent, and is its payout address sanctioned? Checked live against the seller itself plus Chainalysis's sanctions oracle and Blockscout (Base payTo addresses only). Confirms the checkable things about a seller check out -- not a guarantee of trustworthiness, which no free source can promise.

## Output

Returns a structured verification report indicating whether the seller URL responds with a valid 402 challenge, whether the seller's declared input/output schema is internally consistent, and whether the payout address (for Base network) appears on sanctions lists via Chainalysis and Blockscout. Confirms what is mechanically checkable — not a guarantee of full trustworthiness.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "method": {
   "enum": [
    "GET",
    "POST"
   ],
   "type": "string",
   "description": "HTTP method that triggers the seller's 402 challenge."
  },
  "resource_url": {
   "type": "string",
   "description": "The x402 resource URL to verify."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/realx402-seller-754e839e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from goodsong.dev](https://www.zero.xyz/host/goodsong.dev/llms.txt)