Slack webhook payload mapping for Genesys Cloud queue SLA breach

Having some issues getting my configuration to work correctly for sending Slack notifications when a queue SLA is breached. I am using the Genesys Cloud webhook feature to trigger a POST to a Slack incoming webhook URL.

Background

I have a Rails middleware listening for /api/v2/analytics/queue/metrics events. I want to filter for wait_time > sla_target and format a JSON payload for Slack.

Issue

The webhook configuration in Genesys Cloud does not seem to allow complex JSON transformations directly. I am trying to map the metric and queue_name fields into a Slack blocks array structure.

Troubleshooting

Here is the JSON I am attempting to send:

{
 "text": "SLA Breach",
 "blocks": [
 {
 "type": "section",
 "text": {
 "type": "mrkdwn",
 "text": "Queue: {{queue_name}} exceeded SLA by {{wait_time}}s"
 }
 }
 ]
}

The {{queue_name}} placeholder is not being replaced. Does Genesys Cloud webhooks support nested JSON object construction with dynamic values, or do I need to handle this transformation in my Rails middleware before forwarding to Slack?