So, you are writing a novel. As everyone will tell you (including me), you need to have it developmentally edited. But you know what sucks? It can cost a lot of money. Not everyone has that kind of money to put into a book without the promise of a return. Trust me, I get it. That is why many developmental editors now offer something called a manuscript assessment or critique. It can be helpful, whether you are preparing your manuscript for self-publishing or to submit to an agent.
Manuscript assessments are basically a letter from an editor explaining ways to improve the book (developmentally, of course!). They will cover plot suggestions, character development, plot holes, pacing, etc. It is an overview of what the book needs. Usually, when I do a manuscript assessment it comes in the form of a 5-8 page letter (depending on the length of the book).
Personally, I cover as much as I can in the letter, but of course there are limitations. You don't get a full developmental edit from a manuscript assessment. Instead, you get a taste of a full edit. You get the big issues/problems, so that you can improve the book on your own. It is basically getting the professional opinion of an editor on the best ways to improve your book (all condensed into one easy to read 7 page letter!).
Another added benefit, is that you can use the assessment to see if you want a full developmental edit. It is a way to see if you and the editor have similar views on the book, if they get what you are going for, and if they share your vision. It is a cheaper way to see if you want/need more editing done on the book. Many editors (myself included), will discount the price of the assessment from a full developmental edit. This way, you don't have to commit to a full edit, and you can get a taste of it, before making a decision.
Manuscript assessments come in all shapes and sizes, and they can vary from editor to editor. Hopefully, this gives you an overview of what to expect from the editor of your choice. Personally, I find that assessments are a great way to get a lot of bang for your buck and to test the waters. It is a fabulous option!