You asked how to do it with the Execution Link, and that I don't know how to do, (or if it's possible). You have to set up a trigger within the piston of the virtual device "IFTTT". Do you understand how to do that?
And how do you know how to set it up in IFTTT when you don't know how to parse it? It's not the sender that dictates the format, it's the receiver. You have to format it in a way that WebCoRE can read. Do you understand that?
If you follow the steps that I outlined above, each of the things you pass, in my example they were "start", "end" and "description", will parse as arguments. So, you just have to set up some local variables within the piston, and then set the variable equal to the argument.
So, if i were trying to capture the info passes in the this link:
This is the piston i would set up:
Here's a detailed view of the action to set the variable from the argument.
That's all you have to do to get the JSON data out of the link if you send it to webcore that way.