We have an API that expects multiform form-data to upload a file. I'd like to create a stub for it. Is it possible to handle the response differently based on the binary file content?
You can use a Attachment Handler which would extract the content of an attachment from the request message, and then you can add other output tools to that to use the content. To use the content of the attachment for responder correlation, you can use "Custom" to script the condition. Please see the help documentation for "Message Responder Overview" for more information.