API: Improve cli usage descriptions (#4401)

main/commands/all/api/stats_sys.go

@@ -8,14 +8,21 @@ import (
 var cmdSysStats = &base.Command{
 	CustomFlags: true,
 	UsageLine:   "{{.Exec}} api statssys [--server=127.0.0.1:8080]",
-	Short:       "Get system statistics",
+	Short:       "Retrieve system statistics",
 	Long: `
-Get system statistics from Xray.
+Retrieve system statistics from Xray.
+
 Arguments:
-	-s, -server 
+
+	-s, -server <server:port>
 		The API server address. Default 127.0.0.1:8080
-	-t, -timeout
-		Timeout seconds to call API. Default 3
+
+	-t, -timeout <seconds>
+		Timeout in seconds for calling API. Default 3
+
+Example:
+
+	{{.Exec}} {{.LongName}} --server=127.0.0.1:8080
 `,
 	Run: executeSysStats,
 }