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x402 Seller Payability Check
x402
x402 Seller Payability Check is a paid API for AI agents from agent402.tools, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-14).
Tests an x402-protected endpoint end-to-end: decodes the 402 challenge, validates EIP-712 domain/token consistency, attempts a real signed payment, and reports plain-English flags on payability.
Price / call$0.1
Success—
StatusUnknown
How this service works
Buy one call from an x402 seller endpoint right now and report exactly what happened: the unpaid call's status, the 402 decoded (accepts, chains, payTo, asset, price), whether the accept's EIP-712 domain name matches the token it names (the defect that silently makes a whole catalog unpayable), whether a stock client's signed payment was accepted, the settlement receipt and transaction, a slice of the response body, and the time each leg took. Ends in plain-English flags, never a score.
Output
A JSON object containing: plain-English payability flags, the decoded 402 challenge (payTo address, asset contract, price in USD, accepted networks), EIP-712 domain name match verdicts per chain, whether the unpaid call returned 402 correctly, whether a signed payment was accepted, the settlement receipt with transaction hash and payer address, a slice of the paid response body, and millisecond timings for each leg.
Example use cases
Pre-launch x402 endpoint validation
“Before I list my new API at https://api.myservice.com/analyze on a marketplace, can you run a full payability check on it — decode whatever 402 challenge it returns, check for any EIP-712 domain mismatch, actually pay it, and give me plain-English flags if anything needs fixing?”
Debugging a silent catalog unpayability bug
“My x402 endpoint at https://api.example.com/summarize is listed in my catalog but buyers say payments silently fail — can you probe it, decode the 402, and specifically check whether the EIP-712 domain name matches the token it advertises?”
Spot-checking a third-party x402 seller
“I'm about to integrate https://api.thirdparty.com/data/enrich into my agent — can you run a payability check on it using POST, spend at most $0.01, and tell me whether a standard x402 client can successfully pay it and what the settlement receipt looks like?”
Technical details
Endpoint
POSThttps://agent402.tools/api/seller-payabilityWhen to prefer
Use this endpoint when you need to verify that a specific x402-protected API can actually be paid end-to-end by a standard client, especially before listing it on a marketplace or integrating it into an agent workflow. It is uniquely suited for catching the EIP-712 domain name mismatch defect that silently breaks entire x402 catalogs. Prefer it over manual curl-based debugging when you want a structured, machine-readable report with settlement proof and latency data in a single call.
Side effects
- Seller endpoint is unreachable or returns non-402 status on unpaid call — reported in unpaidCall.status
- Payment rejected by seller — settled:false with error details
- EIP-712 domain name mismatch detected — flagged in domainFindings with verdict:'mismatch'
- Seller price exceeds maxUsd cap (default $0.01, max $0.02) — call aborted before payment
- Invalid or malformed 402 response body — readable:false in challenge
- Network or RPC timeout during settlement — payment.error populated
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| url | string | The seller endpoint to check (https), e.g. https://api.example.com/tools/summarize |
| body | object | Optional JSON body the seller's route expects (POST only) |
| maxUsd | number | Most to spend on the seller's own price, default 0.01, capped at 0.02 |
| method | string | GET or POST (default POST) - never a verb that could mutate the seller |
Output
Schema · Response
{
"type": "json",
"example": {
"url": "https://agent402.tools/api/hash",
"flags": [
"a stock buyer can pay this endpoint and get a result: nothing to fix"
],
"method": "POST",
"payable": true,
"payment": {
"ms": 2400,
"error": null,
"status": 200,
"receipt": {
"payer": "0x…",
"network": "eip155:8453",
"success": true,
"transaction": "0x…"
},
"settled": true,
"attempted": true
},
"challenge": {
"asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"payTo": "0x…",
"accepts": [],
"networks": [
"eip155:8453"
],
"priceUsd": 0.01,
"readable": true,
"pricedFrom": "eip155:8453"
},
"checkedAt": "2026-09-11T02:00:00.000Z",
"unpaidCall": {
"ms": 180,
"error": null,
"status": 402,
"bodySlice": "{}",
"contentType": "application/json"
},
"responseSlice": "{\"summary\":\"…\"}",
"domainFindings": [
{
"chain": "Base",
"network": "eip155:8453",
"verdict": "matches",
"expectedName": "USD Coin",
"advertisedName": "USD Coin"
}
]
}
}Tags
x402
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