Embodiments are directed to monitoring for service interfaces. Accordingly, test agent engines may provide a first and a second set of raw data associated with Application Programming Interfaces (APIs) to a test scheduling engine. The test scheduling engine may transform the first and second set of raw data into a first and a second set of reduced data. A quality score engine may aggregate ordinal ranks for the APIs based on the first set of reduced metric data, such that each of the ordinal rankings may be associated with various characteristics of the reduced data. Each of the APIs may be ranked based on their aggregations of the ordinal ranks. A quality score may be provided based on a mapping of the ranked APIs to a distribution model. A second quality score may be generated based on the mapping and the second set of reduced data.