When I run the following mongo shell command against a mongos:

db.runCommand({$query:{usersInfo:1}, $readPreference:{mode: 'primary'}})

I get the response error:

{
	"ok" : 0,
	"errmsg" : "\"$queryOptions\" is not a valid argument to usersInfo",
	"code" : 2,
	"codeName" : "BadValue"
}

I have also observed similar behaviour in NODE-1012.

I do not get such an error when:

• Connecting to a standalone without auth enabled

  { "users" : [ ], "ok" : 1 }

• Connecting to a replica set primary or secondary(1) without auth enabled

  { "users" : [ ], "ok" : 1 }

• Connecting to a replica set primary or secondary(1) with auth enabled and not logged in

  "errmsg" : "not authorized on test to execute command { usersInfo: 1.0} "

• Connecting to a replica set primary or secondary(1) with auth enabled and logged in with appropriate privileges, I get no error and a document containing a list of users and roles

  {
  	"users" : [
  		{
  			"_id" : "admin.limited",
  			"user" : "limited",
  			"db" : "admin",
  			"roles" : [
  				{
  					"role" : "readWrite",
  					"db" : "food"
  				},
  				{
  					"role" : "read",
  					"db" : "foo"
  				}
  			]
  		},
  		{
  			"_id" : "admin.user",
  			"user" : "user",
  			"db" : "admin",
  			"roles" : [
  				{
  					"role" : "dbAdminAnyDatabase",
  					"db" : "admin"
  				},
  				{
  					"role" : "readWriteAnyDatabase",
  					"db" : "admin"
  				},
  				{
  					"role" : "userAdminAnyDatabase",
  					"db" : "admin"
  				},
  				{
  					"role" : "clusterAdmin",
  					"db" : "admin"
  				}
  			]
  		}
  	],
  	"ok" : 1
  }
  

(1) After the obligatory rs.slaveOk() of course.