The following example creates a custom request object with Assign Message:

<AssignMessage name="AssignMessage-3">
  <AssignTo createNew="true" type="request">MyCustomRequest</AssignTo>
  <Copy>
    <Headers>
     <Header name="user-agent"/>
    </Headers>
  </Copy>
  <Set>
    <QueryParams>
      <QueryParam name="address">{request.queryparam.addy}</QueryParam>
    </QueryParams>
    <Verb>GET</Verb>
  </Set>
  <IgnoreUnresolvedVariables>false</IgnoreUnresolvedVariables>
</AssignMessage>

This example:

• Creates a new request message object called "MyCustomRequest".
• On MyCustomRequest, this policy:
  • Copies the value of the user-agent HTTP header from the incoming request to the new message. Because <Copy> uses an absolute reference to the user-agent flow variable, there is no need to specify the source attribute to <Copy>.
  • Sets the address query parameter on the custom message to the value of the incoming request's addy query parameter.
  • Sets the HTTP verb to GET.
• Sets <IgnoreUnresolvedVariables> to "false". When <IgnoreUnresolvedVariables> is "false", if one of the variables the policy tries to add does not exist, Edge will stop processing in the API flow.