Context. Microservice architectures have been growing in popularity for years because they are an effective means to develop scalable and maintainable software. One challenge in developing a microservice architecture is to ensure that the architecture achieves the necessary quality characteristics such as scalability and reliability. Domain-specific languages can be used to model microservice architectures and configure different aspects of them. Problem.Whereby the existing domain-specific languages lack support for quality attributes such as service level objectives. Objective.In this thesis, we present a concept of how such a domain-specific language can be extended to support quality aspects like service level objectives. Method.We developed a prototype using the domain-specific language MDSL, which allows the modelling of service-level objectives. In addition, we have extended the generator for OpenAPI specification, already contained in Microservice Domain-specific Language (MDSL), to support our extensions as well. We validated our approach with an experiment. Result.The results of this experiment show that our prototype has been well accepted by the participants and is a proper tool for specifying quality attributes in microservice architectures. Our extension allows developers to better understand and control their microservice architectures, which improves their reliability and maintainability. Conclusion.In summary, our work demonstrates how important it is to specify quality attributes during the development of microservice architectures and how domain-specific languages can support this process.