Using data from custom fields, in POST to add subscriber to a list

[Dallin Watson]

I want to create a card button that takes information from custom fields such as "email" and send that to Mail Chimp or a Zap webhook to add that email to a subscriber list. 

How can I get that custom field data into the JSON for the button POST action, or is there another way?

[marc]

@Dallin WatsonAs per your question and your tags, I understand you want to use card buttons with butler.

However to use card buttons, you need to program your own power-up.  That's quite a process, described here: https://developers.trello.com/reference#power-ups-intro