# Keystone Opportunity API – x402 Conformance Probe

> Keystone Opportunity API – x402 Conformance Probe is a paid API for AI agents from keystone-opportunity-api.keystone-opportunity.workers.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Validates a live x402-protected URL by probing its HTTP 402 challenge, v2 payment schema, Base USDC amount, payTo/network fields, and OpenAPI price consistency — without making a payment.

## Facts

- Endpoint: POST https://keystone-opportunity-api.keystone-opportunity.workers.dev/v1/x402/conformance
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/keystone-opportunity-api-x402-conformance-probe-81ba1cb3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_-rWCCDC-ExCRv4Y1Oc_Mq

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 keystone-opportunity-api-x402-conformance-probe-81ba1cb3 -d '<json body>'
```

Example prompt: Can you check whether https://api.example.com/premium-data is properly set up as an x402 endpoint — specifically validate the 402 challenge, confirm it's using v2 payment schema, and make sure the Base USDC amount and payTo fields look correct, without actually paying?

## When to prefer this

Use this endpoint when you need to verify that an x402-protected resource is correctly configured before integrating it, debugging payment failures, or running automated conformance checks in CI/CD pipelines. It is the right choice when you want to inspect the live 402 challenge and schema compliance without triggering an actual payment. Prefer this over manual inspection when you also need to cross-reference the live price against an OpenAPI specification.

## Known failure modes

- Target URL does not return HTTP 402 (e.g. returns 200 or 404)
- x402 payment schema is version 1 or malformed instead of v2
- payTo or network fields are missing or incorrectly formatted
- OpenAPI document is unreachable or does not contain price information
- OpenAPI-to-live price mismatch detected
- Target URL is not publicly reachable or times out
- Non-HTTPS URL provided — only public HTTPS resources are supported

## How this service works

Probe an x402 URL without paying it: validate the live HTTP 402 challenge, v2 payment schema, Base USDC amount, payTo/network fields, and OpenAPI-to-live price consistency.

## Output

Returns a structured conformance report indicating whether the target URL correctly returns an HTTP 402 challenge, whether the payment schema matches the v2 specification, whether the Base USDC amount is present and valid, whether the payTo and network fields are correctly set, and whether the live price is consistent with the OpenAPI document.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "format": "uri",
   "description": "Public HTTPS x402 resource to probe without paying."
  },
  "method": {
   "enum": [
    "GET",
    "POST"
   ],
   "type": "string",
   "description": "HTTP method used for the unpaid probe. Defaults to GET."
  },
  "openapiUrl": {
   "type": "string",
   "format": "uri",
   "description": "Optional public HTTPS OpenAPI document. Defaults to /openapi.json on the target origin."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/keystone-opportunity-api-x402-conformance-probe-81ba1cb3/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from keystone-opportunity-api.keystone-opportunity.workers.dev](https://www.zero.xyz/host/keystone-opportunity-api.keystone-opportunity.workers.dev/llms.txt)