i.e., it takes any sentence/phrase as input and automatically figures out the tree diagram.
I'm looking for a way to see the tree structures for sentences/phrases whose tree structures I'm unsure of how to draw.
In short, yes. I assume you're looking to parse English: for that you can use the Link Parser from Carnegie Mellon.
It is important to remember that there are many theories of syntax, that can give completely different-looking phrase structure trees; further, the trees are different for each language, and tools may not exist for those languages.
As a note for the future: if you need a sentence parsed out and tag it as linguistics
(and syntax
or whatnot, if that's available), someone can probably parse it out for you and guide you through it.