Create DRAFT agreement without participants

From a custom application, I'm uploading a transient document and creating a DRAFT agreement, and then display the COMPOSE view so that the user may specify the signers. My problem is that I cannot create the DRAFT agreement without any participants. It seems like the participantSetsInfo is required to have at least one participant. I tried every possible way but unless you specify a participantSetInfo with a least one member with a valid e-mail address, it doesn't work: I get errors such as:

{
     "code": "MISSING_REQUIRED_PARAM",
     "message": "ParticipantSetsInfo Info is missing."
}

Is there a trick by which I could create the agreement wihout participants?