The Idea Validation Filter: How to Know Which Ideas Are Worth Building

Zach gets asked constantly how he came up with the idea for Cal AI. His answer: that is the wrong question. Everyone can come up with ideas. The harder and more valuable skill is knowing which ideas are good and which are bad, so you can filter quickly and commit to the right one.

His personal filter has three layers. First, marketability: can this go viral? Can he see exactly what the TikTok or Instagram ad would look like? If the marketing angle is not obvious, the idea is probably not for him. Second, personal experience: does he use this himself, or does he know people who would? He needs to know specifically who he is building for. Third, adjacent company revenue: is there an existing company in a related space already doing significant revenue? When Zach saw that MyFitnessPal was doing $200 million a year, he knew the calorie tracking market had a proven floor, not a theoretical ceiling.

The adjacent company test is the most counterintuitive part. Most aspiring founders hear "that already exists" and get discouraged. Zach heard it in his university entrepreneurship class — students pitching ideas and classmates immediately saying "that already exists." But competition is validation. If a company in your space is still growing, it means there are still underserved customers. The market is big enough for multiple winners.

Before you have the intuition to assess ideas by gut, you can use objective inputs: TAM of the space, competitive landscape, and the revenue of adjacent companies. But ultimately the filter is personal — what are you good at, what do you know, and what can you market better than anyone else?