# x402 Buyer Shortlist Tool

> 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.

## Facts

- Endpoint: GET https://gpt55.558686.xyz/v1/tools/x402-buyer-shortlist
- Price: $0.005/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-buyer-shortlist-tool-0a961af1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_X5QCKi52ob7XHrDb1yppr

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-buyer-shortlist-tool-0a961af1
```

Example prompt: Can you give me a live-verified shortlist of x402-compatible buyer endpoints from these three origins: https://api.example1.com, https://api.example2.com, and https://api.example3.com — limit to 10 results and use a 5-second timeout?

## When to prefer this

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.

## Known failure modes

- 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

## 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 request

```json
{
 "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
  }
 }
}
```

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "anyOf": [
      {
       "required": [
        "urls"
       ]
      },
      {
       "required": [
        "origins"
       ]
      },
      {
       "required": [
        "discovery_urls"
       ]
      }
     ],
     "properties": {
      "urls": {
       "type": "array",
       "items": {
        "type": "string",
        "maxLength": 2048,
        "minLength": 1
       },
       "maxItems": 10,
       "minItems": 1
      },
      "limit": {
       "type": "integer",
       "maximum": 100,
       "minimum": 1
      },
      "query": {
       "type": "string",
       "maxLength": 120
      },
      "origins": {
       "type": "array",
       "items": {
        "type": "string",
        "maxLength": 2048,
        "minLength": 1
       },
       "maxItems": 10,
       "minItems": 1
      },
      "max_bytes": {
       "type": "integer",
       "maximum": 1048576,
       "minimum": 4096
      },
      "timeout_ms": {
       "type": "integer",
       "maximum": 12000,
       "minimum": 1000
      },
      "verify_limit": {
       "type": "integer",
       "maximum": 10,
       "minimum": 1
      },
      "discovery_urls": {
       "type": "array",
       "items": {
        "type": "string",
        "maxLength": 2048,
        "minLength": 1
       },
       "maxItems": 10,
       "minItems": 1
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "ok": {
       "type": "boolean"
      },
      "tool": {
       "type": "string"
      },
      "fetchedAt": {
       "type": "string"
      }
     },
     "additionalProperties": true
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-buyer-shortlist-tool-0a961af1/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from gpt55.558686.xyz](https://www.zero.xyz/host/gpt55.558686.xyz/llms.txt)