The permissions needed are +connect, +inq and +browse
The +inq authorization has a scope of giving the attributes of the MQ objects and it doesn't necessarily mean that the plugin is getting or reading the actual message in the queue. For the plugin to fetch the message from the queue, it must have the +get authorization which is not required by the MQ-QINFO plug-in.
Below are the details on why the 3 authorizations are required for mq-qinfo plug-in:
+connect - to connect to the queue
+inq - to get the metadata of each MQ object in the queue
+browse - to browse all the messages in the queue and to calculate the message statistics including newest, oldest, and average message ages. Also, for mq-qinfo plug-in to monitor stagnant messages in the queue