# description
PUT /api/domains/:id/webhook — the domain, the stored webhook, and this route's signing secret (returned here so the receiver can verify x-mailkite-signature without a second call).

# properties.domain.description
The domain row (without webhook enrichment — the webhook you just set is alongside).

# properties.routeId.description
The catch-all route (rte_…) that carries this webhook.

# properties.signingSecret.description
This route's signing secret (whsec_…). Store it server-side; verify every delivery.