Yes!!!!!! Especially if this is your first book. If you have already written a best seller, your agent and editor may cut you some slack, if not, that book better be pretty close to perfect or nobody is going to look at it. I know you’ve heard this before if you’ve done any type of research, but agents receive hundreds of queries a week. They don’t have time to read everyone. If your manuscript is full of grammatical and structural errors, that’s all the excuse they need to toss it to the side and move on to the next one.
I sent my first manuscript out to five different agents. I was very excited and a little anxious to hear what they had to say. I expected some rejections but not all. I had put over a year into that novel. It was my baby. Well, two didn’t respond at all, one said no thanks, and another said it wasn’t what they were looking for. The fifth one responded with a rejection but also included a why. There were numerous grammatical and structural errors, I was head hopping and the dialogue dragged.
While I was disappointed, I did take her advice to heart and began the process of editing and correcting structural and grammatical errors. I took two online courses on writing dialogue that moved your story forward. I had never really thought about dialogue moving a story before, but I see it now, and have a pretty good understanding of what the presenters were trying to get across. I also worked on perfecting my POV.
Truth be known, I was ashamed of myself for sending such poor work to an agent. I never realized how bad it was until I began the arduous process of editing and revising. I definitely didn’t make a good first impression.