Abstract: The object of research is the interaction protocols (API - Application Programming Interface) of microservices. The microservices API is an important development object because each microservice can be a client for any other microservice and be created by a separate team. To build a unified system of interaction between microservices, the API-First methodology for synchronizing communication protocols for server applications was used. The aim of the work is to create a way to develop API microservices of server java applications using spring-boot, spring-web, openapi-generator, springdoc libraries. The method is based on the fact that the API is the most important part of the product and therefore is created at the initial design stage. An approach based on a single microservices API and TDD testing technique is proposed, which increases the efficiency of managing the development of server-side java applications. The microservices API is built using the specification as the API artifact. The developed technique allows: use the created API by another team, regardless of the development language; increase the productivity of development teams; to carry out a qualitative description of methods and models; reduce the amount of routine code by generating code from the specification; identify API design errors earlier than with the standard development approach (API after implementation) by applying TDD and working with the API before it is implemented.