My YA manuscript is, by definition, only part one of a larger story I am telling. Though it has a conclusion, of sorts, it also ends on a cliff-hanger. Is this likely to be unattractive to agents?
Yep, a cliff-hanger is pretty unattractive! Sorry, but that’s the case. Bear in mind that if you get a deal for Book 1, the sequel (if we even succeed in selling a Book 2 to the publisher) wouldn’t be out for at least a year after the first. That’s a long time for a reader to wait to know what happens, and your ending is likely to feel disappointing. You should make your story feel like it stands alone, with a satisfying conclusion. That doesn’t preclude a sequel set in the same world/characters.
Hope that helps.