A Cloud Foundry developer is responsible for designing, developing, and deploying applications on the Cloud Foundry platform. They utilize its features to automate, scale, and manage cloud applications. Their tasks include coding in various languages (like Java, Ruby, Node.js), integrating APIs, debugging, and troubleshooting. They also ensure the applications follow the twelve-factor app methodology for scalability and maintainability. They work on microservices architecture and use services like databases, messaging systems, etc. Furthermore, they manage application performance, security, and resource utilization, making sure the applications are cloud-agnostic and resilient.