A Deezer API developer works with Deezer's Application Programming Interface (API) to create and manage applications that interact with the music streaming platform. They use the API to retrieve, manipulate, and display data from Deezer's vast music library, like playlists, albums, or user profiles. They might develop apps that recommend songs based on a user's preferences, create playlists automatically, or integrate Deezer's music into other services. They are responsible for debugging and troubleshooting their applications, ensuring they are reliable and user-friendly. They also need to stay updated with any changes in Deezer's API to maintain the functionality of their apps.