Create custom handler for keepalive check

We have Sensu v0.26.3-1 in one of our critical legacy application running on Ubuntu 18.04. I’m trying to create a custom handler, like below, that will execute a bash script when keepalive fails for a host:

{
  "handlers": {
    "search": {
      "command": "/etc/sensu/plugins/search.sh",
      "type": "pipe",
      "filters": [
        "occurrences"
      ],
      "severities": [
        "critical",
        "unknown",
        "ok"
      ],
      "handle_flapping": false,
      "handle_silenced": false
    }
  }
}

The script ‘search.sh’ is:

#!/bin/bash

# Get HTTP Basic Auth token
TOKEN=$(cat /etc/sensu_svc_account)

curl -X POST https://<redacted> -H "Authorization: Basic $TOKEN" -H "Content-Type: application/json" -d '{ "ruleset": "sensu", "host": "'"$HOST"'", "service": "Keepalive Check", "state": "CRITICAL", "description": "CRITICAL: Keepalive check on '"$HOST"' failed", "service_id": "2677", "alert_source": "SENSU" }' >> /tmp/sensu_nexus_auth.log

echo ' ' >> /tmp/sensu_auth.log

My query:
I want to know how I can pass on the hostname of the host that has failed Sensu’s keepalive check (via $HOST variable) to the bash script.

PS: The format of the POST request needs to be maintained.

Thanks in advance.

Re,