Subscribe to and verify Adobe Acrobat Sign webhooks (current v6 API)

Steps

1. Register a webhook via the Webhooks create operation using an OAuth token with webhook_write scope, supplying webhookSubscriptionEvents (e.g. AGREEMENT_ALL), a scope of ACCOUNT/GROUP/USER/RESOURCE, and either a direct webhookUrlInfo.url or a reference to a previously registered webhook endpoint.
2. Before activating, Acrobat Sign sends an HTTPS GET verification request to your URL with header X-AdobeSign-ClientId set to your app's client ID; your endpoint must return a 2xx and either echo X-AdobeSign-ClientId in the response header or return a matching client-ID field in a JSON body.
3. The same client-ID echo requirement applies to every subsequent POST notification your endpoint receives afterward, not just the one-time verification call.
4. Manage the subscription lifecycle with list/get, update or update-state (requiring an If-Match header for concurrency), and delete operations on the Webhooks resource — each gated by the corresponding webhook_read/webhook_write/webhook_delete scope.
5. Group-level webhooks can only be created by a Group Admin token; account-level webhooks only by an Account Admin token.
6. Confirm current version status before building: Adobe's developer guide still documents both the API Reference and Webhook Reference as v6 with no publicly documented successor version as of this writing.