In the rest api you need to choose a type to execute an command.
[
"action-log",
"admin",
"admin_alias",
"anonftp",
"apache",
"aps",
"autoresponder",
"blupgrade",
"branding",
"branding_theme",
"certificate",
"client",
"client_pref",
"cloning",
"crontab_shell",
"custom_plan_items",
"custombutton",
"database",
"database-registrar",
"database-server",
"dbbackup",
"dns",
"domain",
"domain_addon_service_plan",
"domain_pref",
"domain_restriction",
"domain_template",
"domalias",
"dsn",
"event_handler",
"extension",
"ftpsubaccount",
"grey_listing",
"hotlink_protection",
"http2_pref",
"init_conf",
"interface_template",
"ip_ban",
"ip_pool",
"ipmanage",
"keyinfo",
"license",
"locales",
"mail",
"maillist",
"mailserver",
"migrate",
"nginx",
"notification",
"objectInfo",
"optimization_settings",
"passwords",
"php_handler",
"php_settings",
"pleskbackup",
"pleskrestore",
"poweruser",
"product_info",
"protdir",
"repair",
"report",
"reseller",
"reseller_pref",
"reseller_template",
"role",
"secret_key",
"server_dns",
"server_filesharing",
"server_pref",
"service",
"service_node",
"settings",
"site",
"skeleton",
"spamassassin",
"subdomain",
"subscription",
"task-manager",
"traffic",
"turboaddr",
"user",
"virtdir",
"vps_optimized",
"webstat",
"webuser"
]
one of those types above. Then you can fill in request body params.