A great engineer can build almost any product you describe. That's not the bottleneck in early-stage startups. The bottleneck is understanding which product to build, which customers to prioritize, which iteration is worth making next.
Those questions require market knowledge, not just technical skill. That's founder market fit — and it's different from founder-product fit in ways that matter enormously to outcomes.
The distinction
Founder-product fit: can this person build the thing they're describing? A technical founder who has shipped production systems can build a SaaS platform. Evaluable from a resume and a demo.
Founder-market fit: is this person positioned to win in the specific market they're entering? It requires deep domain expertise in the problem — not research, but lived experience — credibility with the customers they're selling to, and the ability to navigate market nuances that aren't visible from the outside.
A founder who built HFT systems at a quant fund and is now building compliance tools for trading desks has market fit. A founder who read about trading and built the same tool doesn't, even if the technical implementations are identical. The customers can tell the difference in the first ten minutes of a sales call.
The founder who has lived the problem can get their first ten customers from their network. The founder who studied the problem has to earn them from scratch. That's a 12-month advantage.
Eight Capital's three criteria
Deep domain expertise. Not "I've researched this industry." Domain expertise means you've worked in it. Varun Vummadi was building LLMs at Stanford before founding Elise AI. His understanding of what was technically possible — and what the compliance constraints actually were — came from building models, not reading about them.
Relentless grit. Startups fail when founders quit. The founders we back have evidence of persistence through setbacks — they pivoted and survived, they rebuilt after losing a co-founder, they kept shipping after getting ignored at Demo Day. Evidence of past persistence is the best predictor of future persistence.
Ability to raise at least $2M. Not about pitch polish. It's about whether the founder can communicate the vision clearly enough that strangers believe it. A $2M raise proves they can tell the story. It also gives minimum 18-month runway to find out if the thesis is right.
The first customer test
Ask the founder how they got their first paying customer. Founders with market fit almost always describe a customer from their network — a former colleague, an industry contact who had the exact problem. That first customer came through credibility, not cold email.
Founders without market fit describe a long sales process, cold outbound, iterations on the pitch. That's a slower path and the second customer takes longer to find. It's not disqualifying — but it's a different starting position.
The best founders we've backed didn't just build the right product. They were the right person to build in that market. That's the assessment that matters most at seed, when the product is early and the market is still being defined.