How do I assess market demand volume to start API Web3 service for businesses?

So recently, I decided to put my Web3 idea on the market, and I wanted to know the best way to assess market demand. Do I have to email these startups and businesses to know about their interests or anything else? What is the best and most efficient way to do this?

I definitely want to find a statistical way that will give me an overall insight into the market. I appreciate any advice.