In a typical MuleSoft integration project, the role primarily responsible for building API implementations is the API Developer. The API Developer focuses on writing the code that implements the logic, data transformations, and business processes defined in the API specifications. They use tools like Anypoint Studio to develop and test Mule applications, ensuring that the APIs function as required and integrate seamlessly with other systems and services.
While the API Designer is responsible for defining the API specifications and the Integration Architect for designing the overall integration solution, the API Developer translates these designs into working software. The Operations team typically manages the deployment, monitoring, and maintenance of the APIs in production environments.
References
MuleSoft Documentation on Roles and Responsibilities