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x402 Buyer Shortlist Tool
x402
x402 Buyer Shortlist Tool is a paid API for AI agents from gpt55.558686.xyz, paid per call via x402, $0.005/call, status down (last checked 2026-09-15).
Fetches a live-verified shortlist of x402-compatible buyer endpoints or origins by probing provided URLs, origins, or discovery URLs for x402 payment support.
Price / call$0.005
Success—
StatusDown
How this service works
Fetch x402 discovery documents, rank matching resources by advertised price, live-check the cheapest candidates with 402 quote inspection, and return a buyer-ready shortlist with verified amount, scheme, network, payTo, tags, and warnings. This deterministic endpoint does not call an upstream model. GET variant for agents, crawlers, and wallets that prefer query parameters over a JSON body. Pay up to $0.005 per request with x402 USDC on Base.
Output
Returns a JSON object with an 'ok' boolean, the tool name 'x402BuyerShortlist', a summary string confirming live-verified results, and additional fields describing which of the submitted URLs or origins were confirmed to support x402 payments.
Example use cases
Find cheapest x402-enabled API
“I have a list of candidate API endpoints and I want to know which ones actually support x402 payments right now — can you probe these URLs for me and return only the verified ones, ranked by their advertised price from cheapest to most expensive?”
Route payments to verified endpoints
“Before my agent makes any micropayments, I need to confirm which of these origins are actually live and x402-compatible. Can you check https://service-a.io, https://service-b.io, and https://service-c.io and give me a buyer-ready shortlist with their payment amounts, networks, and payTo addresses?”
Audit x402 support across services
“I'm building an x402-aware workflow and I have about a dozen candidate service URLs I found in a discovery document — can you probe all of them for x402 USDC support on Base and tell me which ones pass the live check, along with any warnings I should know about?”
Technical details
Endpoint
GEThttps://gpt55.558686.xyz/v1/tools/x402-buyer-shortlistWhen to prefer
Use this endpoint when you need to programmatically discover and verify which of a set of candidate URLs or origins actively support x402 micropayment flows. It is distinct from general URL fetching — it specifically probes for x402 buyer compatibility and returns a curated, live-verified shortlist. Prefer this over manual probing or generic HTTP tools when building x402-aware agent workflows that need to dynamically route payments to verified endpoints.
Side effects
- No URLs, origins, or discovery_urls provided — request will fail schema validation
- URLs exceed 2048 character limit per item
- More than 10 items submitted in any array — rejected by schema
- timeout_ms out of range (must be 1000-12000) — validation error
- Payment not completed via x402 USDC — 402 response returned, endpoint not called
- Submitted URLs are unreachable or return non-x402 responses — empty or partial shortlist returned
Input
{
"input": {
"type": "http",
"method": "GET",
"queryParams": {
"limit": 10,
"origins": [
"https://api.example1.com",
"https://api.example2.com",
"https://api.example3.com"
],
"timeout_ms": 5000,
"verify_limit": 3
}
}
}Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
{
"ok": false,
"tool": "x402BuyerShortlist",
"query": null,
"warnings": [
"No valid x402 discovery documents were fetched.",
"No priced resources were found.",
"No HTTP resource URLs were available for live quote verification.",
"No candidate passed live x402 quote verification."
],
"documents": [
{
"ok": false,
"error": "`url` host could not be resolved",
"origin": "https://api.example1.com",
"status": 0,
"inputUrl": "https://api.example1.com/",
"serviceName": null,
"discoveryUrl": "https://api.example1.com/.well-known/x402",
"resourceCount": 0
},
{
"ok": false,
"error": "`url` host could not be resolved",
"origin": "https://api.example2.com",
"status": 0,
"inputUrl": "https://api.example2.com/",
"serviceName": null,
"discoveryUrl": "https://api.example2.com/.well-known/x402",
"resourceCount": 0
},
{
"ok": false,
"error": "HTTP 301 non-json",
"origin": "https://api.example3.com",
"status": 0,
"inputUrl": "https://api.example3.com/",
"serviceName": null,
"discoveryUrl": "https://api.example3.com/.well-known/x402",
"resourceCount": 0
}
],
"fetchedAt": "2026-06-12T05:16:13.943Z",
"shortlist": [],
"inputCount": 3,
"usableCount": 0,
"candidateCount": 0,
"validDocuments": 0,
"cheapestVerified": null,
"cheapestAdvertised": null
}Tags
x402
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