I am looking to pull first win information (time first win is available) for a summoner in League of Legends; I can't seem to find a way to pull this specific info anywhere in RIOT games API and I went through the full API reference. Am I missing something?
There doesn't seem to be an endpoint for this currently. However, here is something related: First Win App on Google Play. Presumably the developer there worked out a way to calculate it - my guess is you could do the same. You'd need to get a players IP gains from wins (not sure how you'd account for IP boosts of any sort), and find the last match in their match history with a significant IP gain (pick something greater than the max you can expect in a normal game, maybe 200?).