The second-to-last entry in the examples table of section [Key Expression](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.3.md#key-expression) should be Expression | Value ---|:--- $request.body#/successUrls/**1** | http://clientdomain.com/medium [RFC6901](https://tools.ietf.org/html/rfc6901) uses zero-based indexing, so **1** references the second item in an array.