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FastX402 x402 Payment Header Decoder
x402
FastX402 x402 Payment Header Decoder is a paid API for AI agents from fastx402.tools, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-17).
Decodes a base64-encoded x402 PAYMENT-REQUIRED header into human-readable payment details including network, token, amount, recipient address, and timeout.
Price / call$0.001
Success—
StatusUnknown
How this service works
146 pay-per-call tools for AI agents, from $0.001 per request in USDC on Base or Solana with x402. No account, no API key.
Output
Returns a JSON object with the x402 version, the resource URL, and an array of payment options. Each option includes the asset contract address, human-readable USDC amount, atomic amount, recipient address (pay_to), payment scheme, network identifier (e.g. eip155:8453), network name (e.g. Base), USDC flag, and max timeout in seconds. Also returns an error string if decoding fails.
Example use cases
Inspect 402 challenge before paying
“I just got a 402 response with this PAYMENT-REQUIRED header — can you decode it and tell me which network it wants payment on, how much USDC, and who the recipient is before I go ahead and pay? Header: eyJ4NDAyX3ZlcnNpb24iOjIsInBheW1lbnRzUmVxdWlyZWQiOlt7InNjaGVtZSI6ImV4YWN0IiwibmV0d29yayI6ImVpcDE1NTo4NDUzIn1dfQ==”
Validate x402 header fields in agent pipeline
“Before my agent pays this x402 challenge, decode the PAYMENT-REQUIRED header value and confirm it's requesting USDC on Base with a max timeout of at least 60 seconds. Header: eyJ4NDAyX3ZlcnNpb24iOjIsInBheW1lbnRzUmVxdWlyZWQiOlt7InNjaGVtZSI6ImV4YWN0IiwibmV0d29yayI6ImVpcDE1NTo4NDUzIn1dfQ==”
Explain 402 payment requirement to non-technical user
“I received a PAYMENT-REQUIRED header from an API in base64 and I don't know what it means — can you decode it and explain in plain English what network, token, amount, and address it's asking me to pay to? Here's the header: eyJ4NDAyX3ZlcnNpb24iOjIsInBheW1lbnRzUmVxdWlyZWQiOlt7InNjaGVtZSI6ImV4YWN0IiwibmV0d29yayI6ImVpcDE1NTo4NDUzIn1dfQ==”
Technical details
Endpoint
GEThttps://fastx402.tools/x402-requirements-decode?utm_source=zero.xyzWhen to prefer
Use this endpoint when an AI agent or developer receives an x402 HTTP 402 PAYMENT-REQUIRED response and needs to inspect or explain the encoded payment details before deciding whether or how to pay. It is especially useful for debugging, logging, auditing payment challenges, or presenting human-readable payment info to a user — rather than blindly submitting a payment. Prefer this over manual base64 decoding when you need structured, labelled output with USDC-friendly amounts and network names.
Side effects
- Invalid or malformed base64 input returns an error field in the response
- Missing required 'header' query parameter causes a 400-level error
- Non-x402 or unsupported header format may return empty options array
- Network timeout or service unavailability returns a 5xx error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"error": "Payment required",
"options": [
{
"asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"amount": "0.001",
"pay_to": "0xFe6Ae9ec9DE12817f23958F11b6CE69194b6Bd7E",
"scheme": "exact",
"is_usdc": true,
"network": "eip155:8453",
"network_name": "Base",
"amount_atomic": "1000",
"max_timeout_seconds": 300
}
],
"resource": "https://fastx402.tools/dns?name=example.com",
"x402_version": 2
}
}Tags
x402
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