How do I send the answers collected on a phone call to an outside system with a webhook?

Build it as two flows in the agent's workflow builder.

During the call:

1. Start with a Conversation Started trigger and a Conversation node that greets the caller.
2. Set the Conversation node to auto continue to an Ask and Save node with the questions you need, for example name, email, phone and any custom questions. Every answer is saved to the contact as it is collected.
3. Finish with a Conversation node that says thank you, then a Hang Up node.

After the call:

1. Add a Call Ended trigger.
2. Add an API step set to POST and enter the external system's URL.
3. For the body, post everything from the call and the trigger (as JSON or form fields), or insert only the values you want. Because the answers are saved on the contact, you can insert them as contact variables, such as the contact's first name or website.

The Call Ended trigger already gives you the recording URL, the transcript and a call summary. Do not put an Extract Dynamic Variables step between the Call Ended trigger and the API step. The Call Ended trigger does not open the call recording, so the extraction has nothing to read and the webhook never receives its output. Extraction is meant to run during a live call.