# x402 Endpoint Buyer Preflight

> x402 Endpoint Buyer Preflight is a paid API for AI agents from ai-data-marketplace-1042299154756.us-central1.run.app, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-20).

Probe a live x402-protected endpoint to validate its HTTP 402 challenge, payment requirements, and marketplace listing before authorizing payment.

## Facts

- Endpoint: GET https://ai-data-marketplace-1042299154756.us-central1.run.app/api/v1/x402_endpoint_preflight?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-20
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-endpoint-buyer-preflight-cd990351
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bADv7YUEjmYSkl6M2nvtP

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-endpoint-buyer-preflight-cd990351
```

Example prompt: Before I pay anything, probe https://api.example.com/some-paid-endpoint with a GET request and tell me if its x402 v2 challenge is valid, whether it requires Base network USDC, and if it's actually listed on Coinbase Bazaar or 402index.

## When to prefer this

Use this endpoint when an AI agent or buyer needs to vet an unknown or third-party x402-protected API before authorizing any payment. It is the correct choice when you need zero-cost pre-authorization verification, x402 v2 protocol linting, Base network compatibility checking, or marketplace listing confirmation. Prefer this over blindly calling a paid endpoint or over general HTTP inspection tools that lack x402-specific validation logic.

## Known failure modes

- Target endpoint is not reachable or returns non-402 status — validation cannot proceed
- Endpoint returns a 402 but with malformed or missing x-payment-required headers — lint errors reported
- Endpoint is not listed on Coinbase Bazaar or 402index — listing evidence returns negative
- Network timeout when probing the live endpoint
- Request body forwarding rejected because it contains payment credentials — stripped and flagged
- Endpoint requires a payment method other than Base USDC — flagged as incompatible

## How this service works

Verify and lint a third-party x402 endpoint without paying it. Probe the live HTTP 402 challenge, validate x402 v2 and Base payment requirements, and check exact Coinbase Bazaar and 402index listing evidence before a buyer authorizes payment.

## Output

Returns the parsed HTTP 402 challenge headers and body, x402 v2 protocol conformance results, Base network payment requirement details (token, amount, recipient), Coinbase Bazaar listing evidence, 402index listing presence, and any lint warnings or validation errors — all without forwarding payment credentials or executing a transaction.

## 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",
     "required": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "description": "Public HTTP or HTTPS endpoint to inspect without paying."
      },
      "method": {
       "type": "string",
       "description": "GET, HEAD, or POST. Defaults to GET."
      },
      "request_body": {
       "type": "object",
       "description": "Optional JSON body for a POST probe. Payment credentials are never forwarded."
      }
     },
     "additionalProperties": true
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "required": [
      "success",
      "ready_for_payment",
      "decision",
      "payment_requirements",
      "discovery"
     ],
     "properties": {
      "success": {
       "type": "boolean"
      },
      "decision": {
       "type": "string"
      },
      "discovery": {
       "type": "object",
       "required": [
        "coinbase_bazaar"
       ],
       "properties": {
        "coinbase_bazaar": {
         "type": "object",
         "required": [
          "checked",
          "exact_match_count"
         ],
         "properties": {
          "checked": {
           "type": "boolean"
          },
          "exact_match_count": {
           "type": "integer"
          }
         },
         "additionalProperties": true
        }
       },
       "additionalProperties": true
      },
      "ready_for_payment": {
       "type": "boolean"
      },
      "payment_requirements": {
       "type": "array",
       "items": {}
      }
     },
     "additionalProperties": true
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "success": true,
  "decision": "payment_challenge_is_structurally_ready",
  "discovery": {
   "coinbase_bazaar": {
    "checked": true,
    "exact_match_count": 1
   }
  },
  "ready_for_payment": true,
  "payment_requirements": []
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-endpoint-buyer-preflight-cd990351/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from ai-data-marketplace-1042299154756.us-central1.run.app](https://www.zero.xyz/host/ai-data-marketplace-1042299154756.us-central1.run.app/llms.txt)