I couldn't find specific advice from Tim Ferriss on crafting effective ad scripts. However, generally speaking, Tim Ferriss often emphasizes clarity, brevity, and delivering value in all forms of communication. Applying these principles to ad scripts would involve:

1. Clarity: Clearly state the core message or benefit of the product or service.
2. Brevity: Keep the script concise to maintain the audience's attention.
3. Value: Highlight the unique value proposition and how it meets the audience's needs.

If you need more detailed insights, I recommend exploring various episodes of his podcast or his books where he discusses communication and marketing strategies broadly.