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SignGate Agent Buyer Identity Preflight | x402 Purchase Governance
x402
SignGate Agent Buyer Identity Preflight | x402 Purchase Governance is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.15/call, status unknown (last checked 2026-09-14).
Performs a pre-payment risk assessment for AI agents about to make an x402 USDC payment, checking buyer identity, amount limits, recipient allowlists/blocklists, and approval policies before authorizing the transaction.
Price / call$0.15
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 JSON object containing a risk assessment with a risk_level (e.g. 'low', 'medium', 'high'), a numeric risk_score, an array of flags indicating any triggered policy rules, the network identifier (e.g. 'eip155:8453' for Base), and the product name. This tells the agent whether to proceed with payment, block it, or escalate for human review.
Example use cases
Autonomous agent spending limit enforcement
“My agent with ID agent-prod-007 is about to pay 150 USDC to 0xAb3f9c2d1e4B7a6F0C8d2E5f1A3b4C7d9E0f1A2b for a data enrichment API — can you run a SignGate preflight check with request ID req-spend-001 and nonce nonce-2024xyz to make sure this doesn't exceed our max single payment policy before it goes through?”
Recipient blocklist screening before API purchase
“Before my agent buys access to an x402 API tool from 0x1F2e3D4c5B6a7f8E9d0C1b2A3f4E5d6C7b8A9f0e, run a SignGate payment risk gateway check with agent ID agent-marketplace-1, request ID req-block-scan-99, nonce nonce-blk-55abc, amount 5 USDC, and purpose 'api-tool-purchase' — I want to make sure that recipient isn't on any blocklist.”
Human review escalation for large agent payment
“My AI agent agent-finance-bot is trying to pay 500 USDC to wallet 0xC1d2E3f4A5b6C7d8E9f0A1b2C3d4E5f6A7b8C9d0 for a premium dataset, reference invoice INV-2024-0082, request ID req-large-pay-007, nonce nonce-hrv-9921 — run a SignGate preflight check and flag it for human review if the amount is above our threshold.”
Technical details
Endpoint
GEThttps://base-agent-preflight.bytoken2023.workers.dev/v1/x402/agent/payment-risk-gatewayWhen to prefer
Use this endpoint when an AI agent is about to autonomously execute an x402 USDC payment and you need a policy-aware pre-authorization check before funds move. It is specifically designed for the x402 payment protocol on Base (EVM), supporting recipient allowlists/blocklists, per-transaction amount caps, human escalation thresholds, and audit trails via invoice binding. Prefer this over generic compliance APIs when your agent operates in an x402-native environment and you need lightweight, per-call governance at $0.15 USDC without heavy KYC infrastructure.
Side effects
- Missing required query parameters (request_id, agent_id, purpose, pay_to, amount_usdc, nonce) returns a validation error
- Invalid Ethereum address format for pay_to returns a pattern mismatch error
- Malformed nonce or request_id not matching pattern returns schema validation failure
- Risk score returned as 'high' may block the payment intent without explicit error
- Service unavailable on Cloudflare Workers edge may return 5xx timeout
- Recipient on block_pay_to list results in flagged or rejected assessment
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"network": "eip155:8453",
"product": "agent-payment-risk-gateway",
"assessment": {
"flags": [],
"risk_level": "low",
"risk_score": 0
}
}
}Tags
x402
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