x402station.io API reference

Endpoint state-change watch

Subscribe a webhook to risk-signal state changes for one endpoint.

This HTML page is served by GET /api/v1/watch. The paid API operation remains POST /api/v1/watch.

Signature
POST /api/v1/watch

Pricing
$0.01 USDC for 30 days

Settlement
x402 v2 · exact · Base mainnet USDC

Canonical
https://x402station.io/api/v1/watch

x402 challenge example

HTTP/1.1 402 Payment Required
payment-required: <base64 PaymentRequiredResponse>
www-authenticate: x402
content-type: application/json; charset=utf-8

{
  "x402Version": 2,
  "error": "Payment required",
  "resource": {
    "url": "https://x402station.io/api/v1/watch",
    "description": "Endpoint state-change watch"
  },
  "accepts": [
    {
      "scheme": "exact",
      "network": "eip155:8453",
      "asset": "USDC",
      "amount": "10000",
      "payTo": "0x4053338C7cB38624C0bc23c900F78Cf8470b4E38",
      "maxTimeoutSeconds": 300
    }
  ]
}

Request body

{
  "url": "https://api.example.com/x402-endpoint",
  "webhookUrl": "https://agent.example.com/x402-alerts",
  "signals": [
    "dead",
    "zombie",
    "decoy_price_extreme"
  ]
}

Success response

{
  "watchId": "wch_123",
  "secret": "ws_...",
  "expiresAt": "2026-07-12T00:00:00.000Z",
  "alertsRemaining": 100
}

Error codes

status	meaning
`400`	Malformed JSON body, invalid URL, or missing required field.
`402`	Payment required. Decode payment-required, sign x402, retry.
`503`	Query/probe pipeline timeout. Treat as failed preflight; do not pay target blindly.
`400`	Invalid webhook URL, private-network URL, or unsupported signal.

Notes