Hello @RobertS0822,
Thank you for bringing this to our attention! The response is intended to include an error_key and error_message. I've reported this to our engineers, to be updated.
As you concluded, the 409 error response you received was due to your payload containing a name which was already in use by an existing campaign. As a general reference which may be useful to anyone that comes across this post, our documentation includes a glossary of HTTP response codes, which can be found here: https://developer.constantcontact.com/api_guide/glossary_responses.html
Regards,
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