Finding URL to an OpenAPI version 3.0 specification in JSON or YAML format for connecting to Retool

My company is in the process of integrating Retool into our workflow, and we have identified a critical step that involves obtaining a URL to an OpenAPI version 3.0 specification in either JSON or YAML format. This URL is essential for creating an OpenAPI resource within Retool, as outlined in their documentation here: Retool OpenAPI Integration Guide.

During our internal research, we came across SmartBear SwaggerHub, which is the first result that appears on Google when searching for an OpenAPI URL source. However, even after this discovery, we are still struggling to locate the most basic URL in JSON or YAML format, and we lack clarity on the necessary steps involved.

I am reaching out to the SmartBear Community in the hopes that someone can provide guidance on:

• Where and how to find a basic OpenAPI URL in JSON or YAML format.
  The step-by-step process or best practices for obtaining this URL.

Any insights, tips, or recommendations you can share would be greatly appreciated.