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x402 Base Tools – USDC Authorization Nonce Status & Balance
x402
x402 Base Tools – USDC Authorization Nonce Status & Balance is a paid API for AI agents from base.kagurazaka.dev, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-29).
Checks whether a USDC transferWithAuthorization nonce has been used on Base and returns the authorizer's current USDC balance, letting x402 payment flows confirm settlement.
Price / call$0.001
Success—
StatusUnknown
How this service works
Whether a USDC transferWithAuthorization nonce of an authorizer has already been used on Base, which is how an x402 buyer tells a settled payment from one that never landed, plus the authorizer's USDC balance.
Output
A JSON object with a boolean `used` field indicating whether the nonce has been consumed on-chain, and a `usdc_balance` string showing the authorizer's current USDC balance (e.g. {"used": false, "usdc_balance": "2.89"}).
Example use cases
Confirm x402 payment settlement
“I need to know if the x402 payment from wallet 0xAbCd...1234 with nonce 0x000000...deadbeef has actually settled on Base — did the nonce get consumed?”
Check buyer USDC balance before fulfilling order
“Before I ship the order, can you check if the buyer at 0x9876...fedc has enough USDC on Base and whether their payment nonce 0xfeed...cafe has already been used?”
Audit double-spend attempt detection
“I'm seeing two payment attempts with the same nonce 0x1111...aaaa from authorizer 0x4444...bbbb — has that nonce already been spent on Base?”
Technical details
Endpoint
GEThttps://base.kagurazaka.dev/v1/authorization?utm_source=zero.xyzWhen to prefer
Use this endpoint when building or verifying x402 payment flows on Base and you need to determine in one call whether a specific USDC transferWithAuthorization nonce has been consumed and check the payer's current USDC balance. Prefer it over general blockchain explorers when you need fast, structured JSON output for programmatic settlement confirmation without parsing raw transaction logs.
Side effects
- Invalid or malformed nonce format (not 0x + 64 hex digits) returns an error
- Invalid or non-checksummed authorizer address returns an error
- Missing required query parameters returns a 400-level error
- Network or RPC issues reading Base chain state may cause transient failures
- Nonce or balance data may lag slightly behind the latest block
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"used": false,
"usdc_balance": "2.89"
}
}Tags
x402
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