En example of API documentation tools for your API platforms based on examples of some successful companies:
InPost – uses Confluence

InPost company is using Confluence to describe their shipping API. See example of their documentation here generated from … ?.
Allegro – uses Redoc API

Running API documentation on their own subdomain developer.allegro.pl. See example here.
Also see documentation guild lines. As an API documentation platform, Allegro used Redoc API document generators which support OpenAPI v3 specifications.
Redoc API project GitHub https://github.com/Redocly/redoc
Redocly
Publish classy API docs in seconds
Connect your Git provider or upload your OpenAPI definition, and let Redocly do its auto-magic. Get beautiful and fully featured docs from day one.

Docs: https://redocly.com/docs/
APP: https://app.redocly.com/org
OpenAPI v3 specifications

Swagger – yet another API documentation generator
Yet another tool to generate APP API supporting OpenAPI v3.
https://symfonycasts.com/screencast/api-platform/open-api-spec
https://swagger.io/blog/api-design/openapi-3-0-specification-training/
Read more
https://nordicapis.com/7-open-source-openapi-documentation-generators/