Please provide a command line interface to task library allowing display of task metadata (= what can be seen on http://...//tasks/<taskid>, in test's Metadata or testinfo.desc).

it might work like this:
$ bkr task-details --task=/CoreOS/samba/Sanity/autofs-cifs
Owner:           Ales Zelinka <azelinka>
Name:            /CoreOS/samba/Sanity/autofs-cifs
TestVersion:     1.0
Path:            /mnt/tests/CoreOS/samba/Sanity/autofs-cifs
Description:     mounts a cifs filesystem using autofs
Type:            Sanity
TestTime:        15m
RunFor:          autofs cifs-utils samba samba-client
Requires:        autofs cifs-utils samba samba-client
Priority:        Normal
License:         GPLv2
Confidential:    no
Destructive:     no

Any machine-parsable format (xml) is fine.

We use test metadata quite heavily in BaseOS QE test tiers. Currently we have to download test rpm and extract the testinfo.desc. 

Other use case is integration of Beaker and TCMS: tcms-submit[1] now also uses testinfo.desc directly.

[1] https://wiki.test.redhat.com/BaseOs/Projects/tcms-submit