Here’s how you answer that question in 10 steps:

1. The top five things that differentiate your company from your competition (these must be things that make you different, not better)
2. The specific pain that you solve for your customers
3. No more than eight words that describe how you solve that specific pain
4. The six defining characteristics of your ideal customer
5. Your market size in annual spending on your products/services expressed as ARTS:
   1. Addressable (all customers on the planet who could conceivably buy your products/services)
   2. Relevant (the portion of the addressable market who currently buys your products/services)
   3. Target (your ideal customers)
   4. Serviceable (the customers you could service with your available resources; here assume that you obtained sufficient startup capital to create the minimum business model reflected in your financial projection scenarios)
6. The four reasons your products/services are need to have purchases for your customers (as opposed to nice to have or want to have)
7. The most important customer benefits of your products/services (these must be customer benefits, not product/service features)
8. Your top three barriers to entry (the things that your company has that prevent competitive entry, e.g. intellectual property / patents, technology, sales channels, trade secrets, etc.)
9. The three things that make this new business a low-risk proposition for potential investors
10. One sentence that states the reasons why your founding team are people worth investing in

The answers to those 10 questions will tell you if your startup idea sucks.