You are correct about YAML, but OpenAPI is not YAML -- it just commonly uses it as for the textual representation. As others mentioned it, JSON is an alternative, although it doesn't make it much easier to write the code directly.
Sadly, there is a distinct lack of tools to make spec-first development easier. At the moment, Stoplight [0] is the only game in town as a high quality schema editor, but it requires payment for any more significant usage.
Comments
You are correct about YAML, but OpenAPI is not YAML -- it just commonly uses it as for the textual representation. As others mentioned it, JSON is an alternative, although it doesn't make it much easier to write the code directly.
Sadly, there is a distinct lack of tools to make spec-first development easier. At the moment, Stoplight [0] is the only game in town as a high quality schema editor, but it requires payment for any more significant usage.
[0] https://stoplight.io/