# x402station.io Watch — Webhook Monitoring for x402 Endpoint State Changes

> x402station.io Watch — Webhook Monitoring for x402 Endpoint State Changes is a paid API for AI agents from x402station.io, paid per call via x402, $0.010000/call, status down (last checked 2026-09-15).

Subscribes a webhook to receive HMAC-signed alerts when an x402 endpoint changes state, covering 30 days and up to 100 alerts for $0.01 USDC.

## Facts

- Endpoint: POST https://x402station.io/api/v1/watch
- Price: $0.010000/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402station-io-74590271
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8IjZLN-Cf7oWWFJ1qps2J

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 x402station-io-74590271 -d '<json body>'
```

Example prompt: Set up a 30-day webhook monitor on the x402 endpoint at https://api.example.com/generate so my server at https://my-server.example.com/hooks/x402 gets HMAC-signed alerts whenever its state changes — I want signals for uptime and settlement changes.

## When to prefer this

Use this endpoint when you need ongoing, event-driven notification about a specific x402 endpoint's state rather than a one-time preflight check; ideal for agents that depend on a particular x402 service and need to react automatically to outages, settlement count drops, or behavioral changes over a 30-day window without polling.

## Known failure modes

- Invalid or unreachable x402 endpoint URL — subscription rejected
- Webhook URL not reachable or returning non-2xx — alerts may fail to deliver
- Insufficient USDC payment — subscription not created
- Malformed request body missing required url or webhookUrl fields — 400 error
- Alert quota of 100 exhausted before 30 days — no further notifications sent

## How this service works

Independent risk-signal layer for x402 agentic commerce — endpoint evidence (decoy / zombie / price-trap / never-paid) before an agent authorizes payment.

## Output

A subscription confirmation indicating the watch is active for 30 days with up to 100 HMAC-signed alert deliveries; subsequent webhook POSTs to the provided webhookUrl carry signed payloads describing state changes including settlement count and recency for the monitored x402 endpoint.

## Example request

```json
{
 "url": "https://example.com",
 "signals": [
  "dead",
  "zombie",
  "decoy_price_extreme"
 ],
 "webhookUrl": "https://httpbin.org/post"
}
```

## 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",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "url",
      "webhookUrl"
     ],
     "properties": {
      "url": {
       "type": "string",
       "format": "uri"
      },
      "signals": {
       "type": "array",
       "items": {
        "type": "string"
       }
      },
      "webhookUrl": {
       "type": "string",
       "format": "uri"
      }
     }
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "secret": "a1b2c3d4e5f6...64-char-hex-secret-shown-only-once",
  "signals": [
   "zombie",
   "decoy_price_extreme"
  ],
  "watchId": "0a44f6b8-3b7d-4f2a-9e3a-2c5fd1b0aa11",
  "expiresAt": "2026-05-27T00:00:00.000Z",
  "alertsPaid": 100,
  "endpointKnown": true,
  "alertsRemaining": 100
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402station-io-74590271/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402station.io](https://www.zero.xyz/host/x402station.io/llms.txt)