You should never make a post that is just a link to another site, especially another social media site, with no context. Ideally, your post should give some summary of what is inside the link, and maybe even a TL;DR. I should not need to click or enable previews to find out what your post is about.
Every now and then I look up a tag and there's a number of posts that are just "tumblr url, no reason no context just go to tumblr you dummy" and I'd really like to see less of that. A tag or two doesn't actually tell me what the link is.