In the following example, let's say that a ServiceCallout policy is in the API proxy request, and the callout response contains multiple headers of the same name (Set-Cookie). Assuming the Service Callout's response variable is the default calloutResponse, the following policy gets the second Set-Cookie header value.

<AssignMessage name="AM-Payload-from-SC-header">
  <Set>
    <Payload contentType="application/json">
      {"Cookies from Service Callout":" {calloutResponse.header.Set-Cookie.2}"}
    </Payload>
  </Set>
  <IgnoreUnresolvedVariables>true
  </IgnoreUnresolvedVariables>
  <AssignTo>response</AssignTo>
</AssignMessage>

To list all header values, use the following variable instead:

{calloutResponse.header.Set-Cookie.values}