The KafkaAgent is running inside the Kafka nodes and is used to provide additional information to the Strimzi Cluster Operator about the individual Kafka nodes. It uses port 8443 that is exposed on the Kafka node. We should cover in our documentation that this is exposed and what it is used for - possibly in the https://strimzi.io/docs/operators/latest/full/deploying.html#security-str section where we cover the other ports such as 9090, 9091 etc.