By William Cane
In addition to a table of contents, your book proposal also needs a more detailed outline. Sometimes this is merely called the outline, but I like to call it the chapter-by-chapter summaries. I got this term from literary agent Michael Larsen, and I still think it's a good way to describe this section. The chapter-by-chapter summaries just flesh out each chapter, telling what the chapter will cover. You can do this in a paragraph per chapter.
For a book about vitamins, a chapter-by-chapter summary might look like this:
Introduction. The Introduction will explain why vitamins are recommended as supplements. It will also contain some material describing how I became interested in vitamins.
Chapter 1 - Vitamin A. The merits of Vitamin A are described, along with the most common food sources of the vitamin. The different types of Vitamin A are also described so that by the end of the chapter readers will see how important this vitamin is for human health.
You continue on in this fashion, devoting one paragraph to each chapter.