Explore building service interfaces using OpenAPI/Swagger in this 43-minute conference talk from EuroPython 2016. Discover how to keep track of multiple services and their APIs, solve communication challenges between services, implement request and response validation, and document APIs effectively. Learn from Stephan Jaensch's experience implementing OpenAPI at Yelp, including benefits, generating HTML documentation, and making effortless service calls. Gain insights into overcoming production challenges when scaling to hundreds of services, and understand the OpenAPI initiative's role in creating a vendor-neutral description format. Delve into topics such as Swagger libraries, example specifications, Swagger UI, Zipkin, network issues, client creation, deployment at scale, and testing strategies.