Hosted API Docs Comparison

Swagger
Free tier: 1 user, hosted docs
I think you need to use their Swagger tool to build the API, not recommended

App.stoplight.io
Standard (not white label): $59 p. m.
White label domain etc: $129 p. m.

Readthedocs.com
Standard (not white label): $50 p. m .
White label domain etc: $150 p. m.

Readme.io
Developer $59 p. m.
White label $199 p. m.
Allows creation of an API explorer

Out of the three I’ve seen readme.io implemented the most times and had the most success interfacing with it as a consumer, and would recommend we try them for documentation. They have a free trial.