The best validation signal I've found: can you find 5 people on Reddit/HN/Twitter actively complaining about the exact pain you're solving? Not "it would be nice" — actual frustration posts.

For event schemas specifically, I'd look at how teams currently handle this. If they're writing custom parsers per integration, that's real pain. If they just dump everything into a data lake and query later, the problem might not be painful enough to switch tools.

One thing that worked for me: build the smallest possible version and offer it free to 3 teams. Don't ask "would you use this?" — ask "can I set this up for you right now?" If they say yes and actually use it after a week, you're onto something. If they ghost after day 2, the problem isn't urgent enough.

If someone uses it without you prompting them, then tells a third person — that's usually the clearest signal. The hard part isn't measuring usage, it's whether it spreads without you pushing it.