When using the Zapier integration, the returned JSON is not available as individual fields. For example, the GET call returns the following results:
The data is not available as individual fields when used in the subsequent trigger e.g. FirstName, LastName.
This is because of the way the data is sent back to Zapier. It is controlled by the app on the other side of the webhook, so the format cannot be changed without adding an extra step to the Zap. Using the Zapier formatter app you can extract the data you need.
Set your first Formatter action to look like this:
That'll result in this:
Then add a second Formatter action that looks like this:
That'll result in an output like this which you can then map in your subsequent trigger.