I don’t think doing it in the library is necessary. If someone is using the library directly, they should understand more what they are doing.
But for someone using the uplink CLI to share an object, I think they would appreciate a check to see if the object is accessible at the URL created since the whole purpose is to let someone else access the object. So rather than create an incorrect URL because of a typo (my case) and give it to people in email, give it to a web design group, make it live on a site, etc., the uplink CLI could do an HTTP head request to see if it gets a 200 (success), 404 (not found), or some other status and tell the user:
Test fetch of URL was successful, object size is 24MB (for 200)
Object is not yet loaded at this URL (for 404)
Object is not accessible at this URL: error status 403 Forbidden
I appreciate trying to optimize performance, but in this case, it took me a few minutes to realize what had happened after doing a couple of reloads and getting 404 errors. So I ended up doing extra round trips anyway!