A Xamarin developer is responsible for developing applications that run on the Xamarin platform. The Xamarin platform enables developers to create cross-platform applications using C# and the .NET framework. A Xamarin developer must have a strong understanding of both these technologies in order to be successful. In addition to developing applications, a Xamarin developer also needs to be able to troubleshoot and debug issues that may arise. They need to have strong problem-solving skills in order to identify and fix issues quickly. They should also be able to work well with other team members, as they will often need to collaborate in order to resolve issues.