swagger.io - Swagger is an open source RESTapi Documentation Tool.
Zelle - Zelle is a fast, safe and easy way to send money in minutes to your friends and family.
Slate API Docs Generator - Create beautiful, intelligent, responsive API documentation.
Stripe - Online payment processing for internet businesses. Stripe is a suite of payment APIs that powers commerce for online businesses of all sizes. Use Stripe’s payment platform to accept and process payments online for easy-to-use commerce solutions.
Doxygen - Generate documentation from source code
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