ProgrammableWeb now lists more than 8000+ APIs. The most successful APIs are even billionaires in their own right. We have covered several articles in the past on what are the essential components of a successful API and one pattern that comes out is the need for good developer documentation. In our first annual API survey, the results of which were released in early 2013 showed that the most important factor that developers look out for in an API is good documentation. Adam DuVander wrote an article "Six Ways to Accelerate Time to First Hello World” and having clear and accurate documentation is one of the ways. The task of writing clear documentation for your API is not trivial. But there are a lot of tools available that you could adopt to help automate generation of your API documentation. Gone are the days, where you would simply put up a list of API method calls and sample request/response data. Your API documentation needs to be live where users can punch in request parameters and try out the call. Matt Silverman, Co-founder at Nutritionix.com has written a great summary of the tools available for API documentation. The list is part of his research for generating API documetnation for the Nutritionix API. We have covered Swagger and IODocs in the past. They are great tools to generate professional looking API documentation. Some other tools that come up in the list include apiary.io, Docco, Dexy and Oxygen. What are the tools that you use for your API documentation? How are you pushing the envelope in your API documentation site?