This is to demonstrate the use-case of Overlays for documentation writers.
The original.json file was generated from a swagger-core sample (aka Code-first) and
original.yml is the same definition but in YAML.
This is an effort of using real tools and as close to real issues as possible. Instead of simpler conrvied examples, although going forward simpler examples will be better (for readability at least)!
When we stick this into https://editor.swagger.io we find the following errors...

We also have a little warning where an invalid type is used in an enum...

enum value should conform to its schema's
type.
Adding the Overlay overlay.yml ( should update the definition and produce the following new-openapi.yml. Which addresses the core issues of the generated definition.
- Used https://jsonpath.com/ and https://jmespath.org/ to help test the
targetpaths. - Added
tagswhich felt useful to classifying mutations. Possibly useful to group (and if we need to merge two Overlays into one, tags could be useful in distinguishing). - This example used all pointers to address issues, no "real queries" were needed.
- Lots of opportunites for different tooling to help author Overlays. In this case, it could've been aided by simply "editing the original definition" which instead of mutating the original, should produce an Overlay defintion. Much like a patch file.