# Sentinel Timer – Scheduled Signed Callback

> Sentinel Timer – Scheduled Signed Callback is a paid API for AI agents from sentinel.rootstuff.io, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Schedules a single signed HTTP POST callback to a specified URL at a chosen future time or after a delay, echoing back a custom JSON payload.

## Facts

- Endpoint: GET https://sentinel.rootstuff.io/x402/wake
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/sentinel-timer-scheduled-signed-callback-e09ef70c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_KkOS54cbC6SG0SmC5S1IK

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 sentinel-timer-scheduled-signed-callback-e09ef70c
```

Example prompt: Set a timer to POST to https://myapp.example.com/wake in 3600 seconds with the payload {"job": "send-report", "user": "alice"} so my service wakes up and runs the report job.

## When to prefer this

Choose this endpoint when you need a single one-shot future callback with a signed payload and don't want to operate your own job scheduler or cron infrastructure. Ideal for AI agents, serverless functions, or agentic workflows that need to wake up at a precise future moment without polling. The cryptographic signature on the callback makes it suitable when the receiving service needs to verify the trigger is authentic rather than spoofed.

## Known failure modes

- callback_url is a private/reserved address — request refused immediately
- callback_url contains a redirect — redirects are not followed, delivery may fail
- fire_at is more than 7 days in the future — rejected
- delay_seconds is outside the 10–604800 range — rejected
- payload exceeds 4 KB — rejected
- callback_url is unreachable at fire time — delivery failure, no retry guarantee
- neither fire_at nor delay_seconds provided — request rejected

## How this service works

Timer: one signed callback at a time you choose

## Output

The endpoint confirms the scheduled callback registration. At the specified time or after the delay, Sentinel POSTs the provided JSON payload to the callback_url with a cryptographic signature verifying authenticity. The callback is fired once; no retries beyond what the service guarantees.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "fire_at": {
   "type": "string",
   "description": "ISO 8601 time to fire, within 7 days. Either this or delay_seconds."
  },
  "payload": {
   "type": "object",
   "description": "Up to 4 KB of JSON echoed back in the callback."
  },
  "callback_url": {
   "type": "string",
   "description": "Public https URL that receives the POST. Private and reserved addresses are refused; redirects are not followed."
  },
  "delay_seconds": {
   "type": "integer",
   "description": "Seconds from now, 10 to 604800. Either this or fire_at."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/sentinel-timer-scheduled-signed-callback-e09ef70c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from sentinel.rootstuff.io](https://www.zero.xyz/host/sentinel.rootstuff.io/llms.txt)