Correct syntax to retrieve http response data

I want to use a workflow as a filter to update the price of a Woocommerce product on demand.
I use a hook as a trigger, then an http call and I get a body of type {“key”: value} as a response in Jetflow, but I can’t find the correct syntax to extract the value. I have tried {PREVIOUS.response.key}, {FIRST [response] [“key”]} etc, but I can’t isolate the value from the key.