A JAX-RS developer designs and develops web-based applications using the Java API for RESTful Web Services (JAX-RS). They construct and maintain robust server-side solutions, ensuring seamless data interchange between the server and client-end. They implement HTTP protocol operations, utilizing annotations to simplify HTTP request handling. They also develop code for consuming web services, mapping Java objects to JSON and XML structures. Additionally, they use JAX-RS's client API for communication with RESTful services. Their role involves debugging, troubleshooting, and enhancing application functionality, ensuring optimal performance and user experience, while adhering to industry-standard best practices and protocols.