Final answer:
The author's main purpose in the excerpt from "Tools of the Spymaster" is to inform readers about George Washington's stealth and creativity.
Step-by-step explanation:
The author's main purpose in the excerpt from "Tools of the Spymaster" is to inform readers about George Washington's stealth and creativity. The passage describes how Washington used deception and stealth to fool the British and successfully retreat his army. It showcases the importance of spies and their role in achieving military objectives.