Because it has to be in the body in order to dynamically change it.
When you use the workflow action → TWILIO → bubble will allow you to set dynamic data to the body
You need this to tell the call what’s the current users ‘To’ phone number and also you can change the message that will be sent by changing the “Body”. You can’t set dynamic data to parameters.
First of all you need postman to generate it, get it here: Postman - Chrome Web Store
Here is how you generate it:
It’ll automatically add it to your header.