Microservices are the go-to architectural style for building applications that are polyglot, support high scalability, independent development and deployment, and are rapidly adaptable to changes. Among the core tenets for a successful microservice architecture is high independence of the individual microservices, i.e. loose coupling. A number of patterns and best practices are well-established in the literature, but most actual microservice-based systems do not, as a whole or in part, conform to them. Assessing this conformance manually is not realistically possible for large-scale systems. This study aims to provide the foundations for an automated approach for assessing conformance to coupling-related patterns and practices specific for microservice architectures. We propose a model-based assessment based on generic, technology-independent metrics, connected to typical design decisions encountered in microservice architectures. We demonstrate and assess the validity and appropriateness of these metrics by performing an assessment of the conformance of real-world systems to patterns through statistical methods.