The book Informing the Questioners talks about the books of the Master of Messengers (peace be upon him) on the subject of collecting the honorable Prophet's letters, which are considered historical documents. He also came with the most concise and accurate words, and also contained many words that came in their places, derived from their origins and formulated according to their weights, and this book is considered an invitation book because the dictator of the letters is the Master of Messengers (peace be upon him).