Since we've gained the ability to store arbitrary metadata in the images in the form of labels, I think that it would be nice if we could query the labels without actually downloading neither the image nor the manifest.

/v2/library/repo/labels/?api_version&base

The endpoint would return aggregate label information from all the tags in the given repository:

[
{
     "tag": "latest",
     "digest": "......",
     "labels": {
         "api_version": "v159",
         "base": "centos"
     }
},
{
     "tag": "stable",
     "digest": "......",
     "labels": {
         "api_version": "v134",
         "base": "centos"
}
]

With that I can figure out which image I want to pull without downloading anything (disregarding the inherent race condition in fetch tag list x fetch manifest N ).
For example I can fetch all aggregate VERSION labels and figure out if my local image is up to date.