When the content is structured, the API surface updates, whether it is when new ones come out or old ones are sunsetted, are completely abstracted out from the user - one does not care about method Foo.Bar() becoming Foo.Bar(string param) . This user guarantee is not done exclusively through policy, but rather a combination of policy (API content has to be structured), and format (structured content has a schema) - it’s all defined in a consistent way. Last but not least, a lot of existing tooling that produces API content does so in a way that is already structured.