# Webhook Signature Timestamp Check

> Webhook Signature Timestamp Check is a paid API for AI agents from api.delx.ai, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Validates whether a webhook timestamp is within acceptable age and future-skew bounds before signature verification proceeds

## Facts

- Endpoint: POST https://api.delx.ai/api/v1/x402/webhook-signature-timestamp-check
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/webhook-signature-timestamp-check-d2969676
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_HsfjjGpxXHbI_8KenRoP2

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 webhook-signature-timestamp-check-d2969676 -d '<json body>'
```

Example prompt: Check if this webhook timestamp is valid — the current time is epoch 1720000000, the webhook timestamp is 1719999700, with a maximum allowed age of 300 seconds and a maximum future skew of 60 seconds.

## When to prefer this

Use this endpoint when you need a deterministic, stateless, versioned check of webhook timestamp freshness before proceeding with signature verification — particularly in agentic pipelines where replay attack prevention must be auditable and reproducible without maintaining server-side state. Prefer this over custom logic when you want a normalized, structured evidence trail for compliance or debugging.

## Known failure modes

- Missing required epoch values return an error or undefined behavior
- Maximum age or skew seconds of zero or negative values may produce unexpected results
- If now_epoch is earlier than timestamp_epoch by more than max_future_skew_seconds, advisory/fail status is returned
- Malformed integer inputs may cause parsing errors

## How this service works

Webhook Signature Timestamp Check: Webhook Signature Timestamp Check checks webhook timestamp age and future skew before signature verification from bounded caller-supplied values without an external provider. Call Webhook Signature Timestamp Check before accepting, caching, redirecting, or retrying a caller-supplied web response. Returns normalized web evidence, the computed finding, and an explicit pass or advisory status for Webhook Signature Timestamp Check as versioned deterministic JSON.…

## Output

Returns a versioned deterministic JSON object containing normalized evidence of the timestamp inputs, the computed age and skew values, and an explicit pass or advisory status indicating whether the webhook timestamp falls within the specified bounds.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "now_epoch": {
   "type": "integer",
   "description": "Now Epoch supplied to Webhook Signature Timestamp Check; used only for this bounded calculation and processed in memory without retention."
  },
  "timestamp_epoch": {
   "type": "integer",
   "description": "Timestamp Epoch supplied to Webhook Signature Timestamp Check; used only for this bounded calculation and processed in memory without retention."
  },
  "maximum_age_seconds": {
   "type": "integer",
   "description": "Maximum Age Seconds supplied to Webhook Signature Timestamp Check; used only for this bounded calculation and processed in memory without retention."
  },
  "maximum_future_skew_seconds": {
   "type": "integer",
   "description": "Maximum Future Skew Seconds supplied to Webhook Signature Timestamp Check; used only for this bounded calculation and processed in memory without retention."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": {
   "age_seconds": 120,
   "within_window": true,
   "signature_verified": false
  },
  "schema": "delx/util-webhook-signature-timestamp-check/v1",
  "status": "pass",
  "evidence": {
   "retained": false,
   "input_sha256": "399247a496498846768188f051c797a1de4857867f694fadcc7a0037c29feb35",
   "external_calls": 0
  },
  "operation": "web_reliability:webhook_signature_timestamp_check"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/webhook-signature-timestamp-check-d2969676/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.delx.ai](https://www.zero.xyz/host/api.delx.ai/llms.txt)