In MongoDB 3.0 and earlier, the {netstat:1} command provides a comma separated list of config servers.

For example:

mongos> db.adminCommand({netstat:1})
{
	"configserver" : "config1.example.com:27019,config2.example.com:27019,config3.example.com:27019",
	"isdbgrid" : 1,
	"ok" : 1
}

For backward compatibility with applications that parse this output, it would be great if MongoDB 3.2 clusters continued to support and expose the current list of config servers with this format.