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x402 Payment Guard Preflight Evaluator
x402
x402 Payment Guard Preflight Evaluator is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.100004/call, status unknown (last checked 2026-10-10).
Evaluates an x402 payment URL before autonomous spending — enforcing budgets, scoring merchant/domain risk, detecting replay, and requiring human approval when needed.
Price / call$0.100004
Success—
StatusUnknown
How this service works
Machine-payable service intelligence for discovering, verifying, and monitoring identity, risk, authorization, execution-preflight, and evidence APIs before autonomous agents spend.
Output
Returns a structured decision object containing: a pay/block/hold decision, a risk score for the merchant and domain, payment details parsed from the x402 resource, budget reservation status, policy compliance results, and human-readable reasons explaining the outcome.
Example use cases
Example prompt
“Before paying, run a preflight check on https://api.example.com/report.pdf — use session ID 'sess-abc123' and request ID 'req-001', cap any single payment at 0.50 USDC and the daily budget at 5.00 USDC, and block payments to 0xDeAdBeEf0000000000000000000000000000dEaD.”
Technical details
Endpoint
GEThttps://base-agent-preflight.bytoken2023.workers.dev/v1/x402/payment-guard/evaluate?utm_source=zero.xyzWhen to prefer
Use this endpoint whenever an AI agent is about to autonomously execute an x402 USDC payment and you need to enforce budget caps, block/allow specific recipients, detect replay attacks, score merchant risk, or gate spending on human approval — especially on Base/EVM chains. Prefer this over direct payment execution when operating in autonomous or semi-autonomous agentic workflows where financial guardrails are required.
Side effects
- Missing required query params (url, session_id, request_id) returns 400 validation error
- Budget already exhausted for session returns block decision
- Recipient address on blocklist returns block decision with reason
- Domain risk score too high triggers hold/human-approval decision
- Replayed request_id within session returns replay-detected error
- Invalid URL format or non-https URL rejected by schema validation
- x402 resource unreachable or returns non-402 response causes evaluation failure
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"policy": {
"human_approval": true,
"budget_enforced": true,
"mandate_enforced": true,
"replay_protection": true
},
"payment": {
"pay_to": "0x94F751f04b98507D31b500b7Ed50bE68A1514873",
"network": "eip155:8453",
"amount_usdc": "0.01"
},
"product": "agent-payment-guard",
"reasons": [],
"decision": "ALLOW",
"evidence": {
"domain_risk": "low",
"merchant_risk": "low",
"transaction_simulation": "success"
},
"risk_score": 4
}
}Tags
x402
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