...is that they don't make it clear whether this is fantasy or "based on a true story" historical fiction.

Yes, you said it was "a low-fantasy book" in the post, but there ought to be some clue on the book as well.

"After being unfairly accused and exiled, a swordsman seeks for answers in a troubled country."
I’m confused. Is the swordsman exiled to this "troubled country" or is it the country from which he is exiled and he returns to it? I can’t actually imagine what this story will be about.

"An exiled swordsman seeks revenge against a monarch and peace for his own heart in an unstable country."
Is romance involved? Will there be wangst? The "and peace for his own heart" part is putting me off. Personal preferences. And there is the same confusion as above. So that works worst for me.

"Exiled from a capital governed by the best fighter in the land, a swordsman finds that things aren't as stable as he believed them to be."
This sounds intriguing. I may want to read this.

Sorry, I don’t have more detailed answers to your questions. I hope this helps a bit.

HG

And I don't remember who suggested that, but it wasn't me. Sorry. ^^;

Anyway, I think the third tagline is the best one so far because it's the least generic of the three. The other two, I could have sworn I've heard before in regards to other books, I just can't tell you which ones because they're, well... generic.

Taglines, I feel, should also at least give readers an idea of why this book is different from all the other books with similar plots and themes.