Monitoring with Docker API, no external scripts need. Use {HOST.DNS} for connect to Docker API.

I'm use SSL client certificate to connect to Docker API (here https://dker.ru/docs/component-projects/docker-swarm/configure-docker-swarm-for-tls/ you can found HOWTO). You must specify filename of the client's certificate in {$CERT_FNAME} macro and filename of the client's key in {$KEY_FNAME}. Certificate and key must be in location for SSL client certificate (see SSLCertLocation in zabbix_server.conf)