Who Uses OpenAPI? Since OpenAPI was created as an open format to replace
What OpenAPI Tools Are Available?
An ecosystem of open source and proprietary software has developed around OpenAPI to leverage the machine-readable format of OpenAPI documents. These include tools for generating API reference documentation, creating mock servers, and defining API contracts for automated integration tests, together with validators and linters to ensure specifications adhere to the OpenAPI structure and syntax.
Some of the useful tools for OpenAPI include
https://stoplight.io/studio/ : a free OpenAPI editor, to easily write API descriptions without memorizing syntax.
https://stoplight.io/open-source/spectral/: , an automated validation tool, helps maintain API consistency and style with customizable OpenAPI linting. https://stoplight.io/open-source/prism/ :, a mock server generator, which builds upon your OpenAPI definition to prototype or run integration tests.
Work with your API before you write any code
if you want more detail go to read this article