# x402 URL Liveness Probe

> x402 URL Liveness Probe is a paid API for AI agents from x402.shortforge.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-31).

Given a public HTTP(S) URL, returns a structured liveness verdict (LIVE, PAUSED, GATED, CHALLENGED, DEGRADED, DEAD, or UNKNOWN) with sourced reasons explaining the status.

## Facts

- Endpoint: GET https://x402.shortforge.dev/x402/probe?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-url-liveness-probe-0e9e2b26
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_njRR6F_g8wtHfTcB4JYzx

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-url-liveness-probe-0e9e2b26
```

Example prompt: Can you probe https://api.example.com/health with a GET request and tell me whether it's actually live, or just pretending to be up — I want the full verdict with reasons?

## When to prefer this

Choose this endpoint when you need to go beyond a naive HTTP status check and detect subtle failures like a gateway returning 200 while the upstream service is dead, or when you need a machine-readable categorical verdict with sourced evidence. Ideal for agent workflows that gate on real service availability before making downstream calls, monitoring pipelines, or any situation where a simple ping is insufficient.

## Known failure modes

- Invalid or non-public URL returns an error or UNKNOWN verdict
- URL behind a firewall or IP block may return DEAD incorrectly
- Very slow endpoints may time out and return DEGRADED or UNKNOWN
- Redirecting URLs may require following chains not captured in a single probe
- Endpoints requiring POST or non-supported methods cannot be probed (only GET/HEAD/DELETE supported)

## How this service works

Given any public HTTP(S) URL, returns a measured liveness verdict - LIVE, PAUSED, GATED, CHALLENGED, DEGRADED, DEAD or UNKNOWN - with every reason carrying the source it was read from. The point is the case a status check misses: a front door answering 200 over a back end that stopped. Also sold at this origin: good ($149.00, POST /x402/good) - The x402 rail, ninety days - framed print, 24 x 36 in; census ($100.00, GET /x402/census) - The x402 rail census, ninety days, whole.

## Output

A structured liveness verdict object with one of seven categorical labels (LIVE, PAUSED, GATED, CHALLENGED, DEGRADED, DEAD, UNKNOWN), accompanied by a list of reasons each tagged with the source from which the evidence was read. This goes beyond a simple HTTP status code check by detecting cases where a front-end proxy answers 200 while the back end is non-functional.

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "queryParams": {
     "type": "object",
     "required": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-url-liveness-probe-0e9e2b26/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.shortforge.dev](https://www.zero.xyz/host/x402.shortforge.dev/llms.txt)