If you recently played with the person but didn't get their tag, check the "Recent Players" list in the People tab. This is often faster than typing out a complex gamertag.
Searching for an Xbox gamertag is primarily done through the console's social menu or the official Xbox mobile app. While third-party "lookup" tools exist, they are often reviewed as less reliable than official methods for real-time accuracy and privacy. gamertag xbox search
Simply tap the Search icon and toggle the filter to "People" to find friends or new competitors. If you recently played with the person but