Have you taken a look at the following?

Avamar 7.1 Management Console Command Line Interface (MCCLI) Programmer Guide

That would be the first resource to consult as it has many examples and syntax.  If you ever don't have that to hand you can also get contextual syntax tips by appending --help to any mccli command

For example

mccli backup show --help

backup show: Show a client's backups

                        [--after=String]:       Absolute date of filter (format: YYYY-MM-DD)

                        [--before=String]:      Absolute date of filter (format: YYYY-MM-DD)

                        [--contained-vm-name=String]:   VM/vAPP name inside the Container

                        [--dir=String]:         Directory of backup to start viewing

                        [--domain=String(/)]:   Client's domain

                        [--labelNum=Integer]:   Label number of backup

                        <--name=String>:        Client's name

                        [--recursive=Boolean(false)]:   Recursively show backup directories and files

                        [--retention=String]:   Retention type filtering, format=r{,r}* where r={N|D|W|M|Y|none|daily|weekly|monthly|yearly}

                        [--verbose=Boolean(false)]:     Show verbose details

You could also run an advanced search on all Avamar articles containing mccli.  The following query currently brings back 133 articles.. plenty of examples and tips in there

https://support.emc.com/search?text=mccli&resource=SOL&adv=y&kbAdv=y&kbDatescParam=