A sales brief exists to be read in the five minutes before a call. It is not a research dump, and it is not a company profile. It answers four questions: why this company, why now, who matters and what to say.
A useful brief separates what is known from what is guessed. Facts carry a source. Inferences are labelled as inferences, so a seller knows what they can state out loud and what they need to confirm in the conversation.
A Buzzlist Sales Brief runs to twelve sections and is built from public research. You can read a real one here.