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Agent402 Webhook HMAC Signature Verifier
x402
Agent402 Webhook HMAC Signature Verifier is a paid API for AI agents from agent402.tools, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).
Verifies webhook HMAC signatures for GitHub, Stripe, Shopify, and Slack using each provider's exact signing scheme, including replay protection.
Price / call$0.001
Success—
StatusUnknown
How this service works
Verify a webhook's HMAC signature against the correct per-provider scheme: GitHub (X-Hub-Signature-256, sha256=hex), Stripe (Stripe-Signature t/v1 over "<t>.<body>" with replay tolerance), Shopify (X-Shopify-Hmac-Sha256, base64), Slack (X-Slack-Signature, v0:<ts>:<body> with replay tolerance). Constant-time comparison; the secret is never echoed. Pass the RAW request body string - signatures are over the raw bytes. Deterministic.
Output
Returns whether the HMAC signature is valid or invalid for the given provider's scheme, incorporating timestamp-based replay protection for Stripe and Slack. The signing secret is never echoed back in the response.
Example use cases
Example prompt
“Can you verify this incoming Stripe webhook for me? The raw body is '{"id":"evt_123","type":"payment_intent.succeeded"}', the Stripe-Signature header is 't=1714000000,v1=abc123def456', my webhook secret is 'whsec_mysecretkey', and the timestamp is '1714000000' — use a 300-second replay tolerance.”
Technical details
Endpoint
POSThttps://agent402.tools/api/webhook-verifyWhen to prefer
Use this endpoint when you need to cryptographically verify that an incoming webhook genuinely originated from GitHub, Stripe, Shopify, or Slack — especially when you want to avoid implementing each provider's specific HMAC scheme (sha256 hex for GitHub, timestamped HMAC for Stripe, base64 HMAC for Shopify, v0= scheme for Slack) and replay-attack protection yourself.
Side effects
- Invalid or mismatched signature returns a failed verification result
- Timestamp outside tolerance window triggers replay protection failure for Stripe/Slack
- Missing required timestamp for Stripe or Slack causes error
- Unknown provider value returns an error indicating unsupported provider
- Malformed signature header format causes parsing error
- Raw body was re-serialized (not byte-for-byte original) leading to false negative
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| secret | string | the provider signing secret (never echoed back) |
| payload | string | the RAW request body string, byte-for-byte as received (never a re-serialized object) |
| provider | string | github | stripe | shopify | slack |
| signature | string | the signature header value, with or without its scheme prefix (sha256= / v0= / t=...,v1=...) |
| timestamp | string | provider timestamp, required for stripe + slack (stripe may be parsed from a t= element in the signature) |
| toleranceSeconds | number | max timestamp age for stripe/slack replay protection (default 300; 0 skips the age check) |
Output
Schema · Response
{
"type": "json",
"example": {
"valid": true,
"reason": "signature matches the recomputed HMAC for this payload and secret",
"scheme": "X-Hub-Signature-256: sha256=hex(HMAC-SHA256(secret, rawBody))",
"provider": "github"
}
}Tags
x402
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