Requires pipeline_id, stage_id, and at least one organization_ids entry. Stage must belong to that pipeline. organization_ids attaches CRM rows via organization_deal (deal has no organization column); optional lead_ids / contact_ids are independent many-to-many links; optional tag_ids links tags via deal_tag in the same transaction. Notes are not created here—use POST .../notes or read them via GET .../deals/:id relationship previews.