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x402station.io Watch — Webhook Monitoring for x402 Endpoint State Changes
x402
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.
Price / call$0.010000
Success—
StatusDown
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 use cases
Monitor third-party vendor API for payment disruption
“Watch the x402 endpoint at https://vendor.api.example.com/checkout for the next 30 days and send HMAC-signed alerts to https://my-backend.example.com/webhooks whenever it goes down or stops settling payments — I need to know immediately if our checkout integration breaks.”
Track suspicious endpoint behavior before trusting transfers
“Subscribe to alerts on https://payments.competitor.example.com/process so I can catch if it starts acting like a decoy or zombie endpoint — send HMAC-signed notifications to https://agent-monitor.example.com/x402-alerts whenever settlement count drops or behavior changes in the next month.”
Detect when a marketplace vendor becomes unreliable
“Set up a 30-day webhook subscription on https://marketplace-vendor.example.com/api/pay and alert my ops team at https://ops.example.com/risk-signals whenever the endpoint shows signs of never paying out or changes its settlement pattern — I want those HMAC-signed notifications so we can delist risky vendors early.”
Technical details
Endpoint
POSThttps://x402station.io/api/v1/watchWhen to prefer
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.
Side effects
- 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
Input
{
"url": "https://example.com",
"signals": [
"dead",
"zombie",
"decoy_price_extreme"
],
"webhookUrl": "https://httpbin.org/post"
}Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
{
"secret": "2c6e5349eb4ee2c4ceff50ade5238ebca45dabbadca4824d8a7cef8116cb7d9e",
"signals": [
"dead",
"zombie",
"decoy_price_extreme"
],
"watchId": "fe43924e-f336-453c-8bd8-b7e83d039938",
"expiresAt": "2026-06-28T20:50:13.117Z",
"statusUrl": "/api/v1/watch/fe43924e-f336-453c-8bd8-b7e83d039938?secret=<secret>",
"alertsPaid": 100,
"attribution": {
"url": "https://x402station.io",
"spec": "https://x402station.io/spec",
"claim": "machine-readable response provenance, not merchant endorsement",
"product": "Watch by x402station.io",
"authority": "x402station.io"
},
"endpointKnown": false,
"deliveryFormat": {
"method": "POST",
"headers": {
"content-type": "application/json",
"x-x402station-alert-id": "<bigint>",
"x-x402station-watch-id": "<watch uuid>",
"x-x402station-signature": "sha256=<hmac-hex>"
},
"retryPolicy": "Up to 5 attempts with ~5min spacing (driven by the watch-tick cron). After 5 failures the alert is marked failed and not retried.",
"examplePayload": {
"alertId": 42,
"watchId": "<uuid>",
"priorState": {
"signals": [],
"checkedAt": "2026-04-27T00:50:00.000Z",
"priceAmount": "0.001"
},
"endpointUrl": "https://example.com/",
"currentState": {
"signals": [
"zombie",
"no_history"
],
"checkedAt": "2026-04-27T01:00:00.000Z",
"priceAmount": "0.001"
},
"firedSignals": [
"zombie"
],
"clearedSignals": [],
"alertsRemaining": 99
},
"signatureScheme": "HMAC-SHA256 over the raw request body, hex-encoded; verify with the secret returned above. Constant-time comparison required."
},
"unsubscribeUrl": "/api/v1/watch/fe43924e-f336-453c-8bd8-b7e83d039938?secret=<secret>",
"alertsRemaining": 100,
"idempotentReplay": false
}Schema · Response
{
"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
}
}Tags
x402
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