I have been working in API.AI for a while and jumped back into it yesterday some. I want to describe what API.AI is and what it isn't so that there is a clearer picture of it. I am attaching a sample api.ai project that you can use to start building from if you would like to do so.
First, what is it? API.AI is great at taking speech and breaking it down to give you the intent behind the speech. For example, in the example, you can say something like "Hey Robot, I want you to raise your right arm 19 degrees". The returned text (what would be returned to EZ-Builder) is "[Movement] [RightArm] [up]  [deg]".
You can use a script to break down what the robot is being asked to do from the information above. The phrase "yo, raise your right arm 1 degree" would also work and return "[Movement] [RightArm] [up]  [deg]" for you to parse and use.
There are some chatbot features called "SmallTalk". This works like any other chatbot and takes questions or statements from the user and returns text that you want it to return. This is the simplest form of using API.AI and probably is the easiest part of it, but is also not the most useful.
There are some prebuilt agents. These agents each use their own API key. Because of this, I don't recommend using them because the plugin only allows one API key, and you will quickly run out of allowable uses. It is far better to build a single customized agent which contains everything that you want your robot to use.
The use of this tool is to break apart and parameterize language. This allows you to use completely different speech for specific commands in EZ-Builder. Currently, the plugin only sets 2 variables in EZ-Builder. This requires that you pass the parameters in API.AI back in the Text response field that would match the layout of what you want to parse.
The example here doesn't use integrations, but is designed more to have the information sent back to ARC for you to do something with.
This is a very scaled down version of the Rafiki client that I had been working on.
You can take this and import or restore it into your api.ai project.
I hope this example helps people see what API.AI can be used for and better understand where it fits in your robot brain.