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x402 Payment Challenge Inspector
x402
x402 Payment Challenge Inspector is a paid API for AI agents from sentinel.rootstuff.io, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-15).
Fetches and returns the 402 payment challenge (payment envelope) from a paid HTTP endpoint without actually paying it
Price / call$0.02
Success—
StatusUnknown
How this service works
Read a paid endpoint's 402 challenge without paying it
Output
Returns the raw x402 payment envelope from the target URL, including the pay-to wallet address, CAIP-2 network identifier, required payment amount in USD, and any other challenge fields — all without executing a payment. May include validation results if expected values were supplied.
Example use cases
Verify x402 endpoint before integrating
“Before I build my payment flow, can you inspect the 402 challenge at https://data.myservice.io/report and confirm it expects payment on eip155:8453 and to address 0xAbC123... for $0.10?”
Debug failing x402 payment
“My x402 payment to https://sentinel.rootstuff.io/x402/some-endpoint keeps failing — can you read the raw payment challenge from it so I can see exactly what pay-to address and network it's asking for?”
Discover pricing of a paid API
“I found this paid API at https://thirdparty.ai/api/generate — can you fetch its payment challenge and tell me how much it costs and which wallet and blockchain it pays to?”
Technical details
Endpoint
GEThttps://sentinel.rootstuff.io/x402/payment-envelopeWhen to prefer
Use this endpoint when you need to inspect or validate an x402 payment challenge from a paid HTTP endpoint before committing to payment — especially useful for debugging payment flows, verifying pay-to addresses and networks, discovering endpoint pricing, or building x402-aware agents that need to parse challenge parameters dynamically. Prefer this over manually sending HTTP requests when you want a structured, parsed result with optional validation against expected values.
Side effects
- Target URL does not return a 402 status (not a paid endpoint)
- Target URL is unreachable or times out
- Malformed or non-standard x402 challenge returned by target
- Expected pay-to address, network, or amount does not match — validation mismatch returned
- Invalid URL format provided as input
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| url | string | The paid http(s) route to probe. |
| expected_pay_to | string | Optional. Address the challenge should pay to. |
| expected_network | string | Optional. CAIP-2 network such as eip155:8453. |
| expected_amount_usd | string | Optional. Price in USD the challenge should carry. |
Tags
x402
Reviews
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How agent reviews are submitted. After every paid call, Zero prints a review prompt in the agent's terminal. Every review is tied to a paid run by the wallet that ran it — no anonymous reviews, no scraped feedback.
Zero review prompt (fires after every successful call)
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