x402 · agent safety
x402 payment scanner: check a 402 endpoint before you pay
The x402 payment scanner reads an endpoint’s payment request and tells you what an AI agent would be signing: the price, the token, the network, who gets paid and for how long the signature stays valid. Look before your agent pays. Nothing is paid, nothing is signed and no wallet is needed.
What it checks
Six questions about one payment request
An agent that pays over x402 signs whatever the seller’s 402 answer asks for. These are the parts of that answer that decide whether signing is a mistake.
Is the token really USDC?
The seller names the token contract your agent is asked to sign for. The scanner compares it with the USDC contract for that network. A token it does not recognise is high risk, because signing for an unknown contract is a common way wallets are drained.
How long does the signature live?
An x402 payment is a signed permission with an expiry. Over five minutes is flagged. Over an hour is high risk: a signature that long can be used well after you stopped expecting it.
Who gets paid?
The payout address is checked against sanctions and scam lists, and for addresses nobody can spend from, such as the zero address. The scanner also reports whether the address is a contract or a plain wallet.
Is it the site you think it is?
A payment request names the address it is for. If that is a different site from the one you asked, or the name uses lookalike characters, the scanner says so.
What does it cost?
The price is shown in US dollars. Anything above one dollar gets a note, since most pay-per-call endpoints cost a few cents.
What could not be checked?
If a list is unavailable, the network is one the scanner does not know, or the endpoint does not answer, the result says careful. Unknown is never reported as safe.
x402 payment scanner: questions
The x402 payment scanner is a free tool from SpendTheBits that reads the payment request of any x402 endpoint before an AI agent pays it. You paste the address, the scanner asks the endpoint once for its 402 Payment Required answer, and it shows the price, the token, the network, the payout address, how long a signed payment would stay valid, and anything in the request that looks risky.
No. The scanner sends one ordinary unpaid request, the same one any x402 client sends first, and stops there. It holds no wallet, signs nothing and pays nothing, so a scan cannot cost you money.
High risk means at least one finding is a known way to lose money, such as an unrecognised token, a payout address on a sanctions or scam list, or a signature that stays valid for more than an hour. Careful means something is unusual or could not be checked. Clear means every check ran and none of them fired.
No. A clear result means the payment request itself has none of the problems the scanner looks for. It says nothing about whether the seller delivers what was promised, so an agent should still have a spending limit and an owner who can see what it paid.
Nothing about the scan. The address you paste and the result are not stored. Your network address is counted for ten minutes, only to enforce the limit on scans, and is not kept after that.
Five scans every ten minutes. The limit exists because each scan makes our server visit an address a stranger chose, and that must not become a tool for bothering other sites.
Any public https endpoint that answers 402 Payment Required with an x402 version 1 or version 2 payment request. The scanner does not follow redirects and does not visit private or local addresses.