sent-webhook-engineer
Installation
SKILL.md
Sent Webhook Engineer
Sent webhooks are the only way an application learns what happened after POST /v3/messages returns 202. The 202 proves acceptance, never delivery. Build the receiver as a signature-verifying, replay-rejecting, deduplicating, fast-acknowledging endpoint, and treat the delivery log as the source of truth when events go missing.
Signature verification, exactly
Three headers arrive with every delivery:
| Header | Meaning |
|---|---|
x-webhook-signature |
v1,{base64(hmac_sha256)} |
x-webhook-id |
The webhook endpoint UUID — identical on every delivery |
x-webhook-timestamp |
Unix seconds when Sent signed the request |
Verification procedure, in order: