REST API (Representational State Transfer Application Programming Interface) is a set of rules and protocols that facilitate interaction between different software components over the internet. As part of the tech skills set, mastery in REST API allows developers to create, read, update, or delete information between different software services seamlessly, providing a way for systems to communicate with each other.

Companies using REST API in their operations have the advantage of this protocol being stateless, which means every HTTP request happens independently. Information is transferred in a standardized way, typically in XML or JSON format, enhancing scalability and performance while maintaining simplicity and readability. These features make REST a popular choice for developers and companies working on public APIs for their services.

As a potential candidate for a job role requiring the use of REST API, one should have a comprehensive understanding of HTTP methods such as GET, POST, PUT, PATCH, and DELETE. Familiarity with status codes, error responses, and HTTP authentication give added value to your competency in this area. In-depth knowledge is required in constructing RESTful services and understanding the data transfer processes between a client and a server.

Working proficiency in programming languages such as Python, Java, or JavaScript is essential as REST APIs are language-agnostic. Experience with web services and API integration, as well as the understanding of JSON or XML is also crucial. Furthermore, knowledge of software testing and debugging is helpful for roles involving REST API. Certification in REST API design can also enhance employability.

To master REST API, having a strong foundation in web development, specifically with regard to server-side technologies, is immensely beneficial. Solid understanding of HTML, CSS, and JavaScript, as well as laying hands-on server-side languages is a great jumping-off point. Experience with databases and query languages, knowledge about client-server architecture, and general understanding of internet protocols all combine to provide a well-rounded base for diving into REST API. Prospective learners should also hold the ability to solve problems and think logically as the use of REST APIs could present complex situations that require innovative solutions.

In summary, REST API is a critical skill in the toolkit of modern web developers and software engineers. Its mastery opens the door to improved system integrations and more efficient, scalable applications.