JetBrains development tools like IntelliJ IDEA, PyCharm and others come with a bundled *OpenAPI Specifications* plugin.
The plugin allows you to write the OpenAPI specifications and supports you with validations, formatting, code-completion etc.
It supports a *text view* as well as a rendered SwaggerUI-like *graphical interface*.
Stoplight Studio is a GUI/text editor with linting and mocking built right in. It can run on the desktop with local files, and in the browser powered by your existing GitHub, GitLab, or BitBucket repos.
Zuplo is an API gateway designed for developers. Natively powered by OpenAPI (3.1 or 3.0), zuplo offers an OpenAPI design surface, API documentation and a serverless, programmable edge gateway that includes request validation, auth, rate-limiting and more.