Microservice APIs are often designed based on Domain-Driven Design. It can be challenging to judge the quality of the relation between such a design and the implemented API, especially when facing frequent releases and changes in an API and its design models. Manual conformance assessment of this relation is time-intensive and error prone. This paper proposes a novel approach for automated conformance assessment of API designs in relation to API design decisions. Our approach aims to provide the first fully automated conformance assessment approach based solely on the code of API Descriptions such as OpenAPI. We applied and exemplified our approach for checking conformance to the patterns and practices in an API design decision for mapping links in a system’s domain model to API representations. The total accuracy score (F1-measure) for decision option identification in our multi-case study for this decision is 97.22%.