# x402 Delayed HTTP Callback Scheduler

> x402 Delayed HTTP Callback Scheduler is a paid API for AI agents from x402-paywall.huntercarver24.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-31).

Schedules a one-time delayed HTTP callback to any public URL, firing a GET or POST request after a specified delay (60 seconds to 7 days) or at an absolute time, with one retry and a 10-second timeout.

## Facts

- Endpoint: POST https://x402-paywall.huntercarver24.workers.dev/later?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-delayed-http-callback-scheduler-1bb36925
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_TegNk7xwOYZmjOZS_ILJm

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-delayed-http-callback-scheduler-1bb36925 -d '<json body>'
```

Example prompt: Schedule a delayed callback to https://myapp.example.com/webhook in 90 seconds — send a POST with the JSON body {"event": "reminder", "userId": "u123"} and include an Authorization header of 'Bearer abc123'.

## When to prefer this

Use this endpoint when you need to fire a one-time HTTP callback to a public URL at a precise future time or after a specified delay, without running your own cron infrastructure. Ideal for webhook-based workflows, post-processing triggers, or timed notifications in serverless or agent pipelines. Prefer this over polling-based approaches or custom scheduled jobs when you need a lightweight, pay-per-use scheduled HTTP call with delivery confirmation.

## Known failure modes

- Private, local, or cloud-metadata target URLs are refused at scheduling and again at fire time
- Redirects from the target URL are reported but not followed
- Callee does not respond within 10-second timeout — one retry is attempted
- Body exceeds 65536 bytes serialized
- More than 16 custom headers provided
- Header values contain non-printable ASCII or exceed 1024 characters
- Forbidden headers (host, content-length, connection-level) are rejected
- Both delaySeconds and at are provided simultaneously — refused
- Delay is less than 60 seconds or more than 7 days (604800 seconds)

## How this service works

Schedules a delayed HTTP callback: give a public URL, an optional JSON body, optional headers and a delay of 60 seconds to 7 days (or an absolute time), and this host calls the URL at that time (POST when a body was given, otherwise GET), with one retry and a 10-second timeout. GET /later/<id> reports whether it fired and the status code the callee answered. A request that is refused is not charged.

## Output

Returns a callback ID on successful scheduling. A GET to /later/<id> returns whether the callback has fired and the HTTP status code returned by the target URL. If the request was refused (invalid URL, private address), it is not charged.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "at": {
   "type": "string",
   "format": "date-time",
   "description": "Absolute time with a timezone, e.g. 2026-10-28T15:00:00Z, 60 seconds to 7 days ahead. Give this or delaySeconds, not both."
  },
  "url": {
   "type": "string",
   "format": "uri",
   "description": "Public http(s) URL to call. Private, local and cloud-metadata addresses are refused, when scheduled and again when fired. Redirects are reported, not followed."
  },
  "body": {
   "description": "Any JSON value. Present: the callback is a POST with this as its JSON body. Absent or null: a GET. Up to 65536 bytes serialised."
  },
  "headers": {
   "type": "object",
   "description": "Extra request headers, printable ASCII values up to 1024 characters. host, content-length and connection-level headers are refused.",
   "maxProperties": 16,
   "additionalProperties": {
    "type": "string"
   }
  },
  "delaySeconds": {
   "type": "integer",
   "maximum": 604800,
   "minimum": 60,
   "description": "Seconds from now. Give this or at, not both."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-delayed-http-callback-scheduler-1bb36925/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-paywall.huntercarver24.workers.dev](https://www.zero.xyz/host/x402-paywall.huntercarver24.workers.dev/llms.txt)