Create a contact and, in the same call, log its first note and/or first interaction — the composite first-touch door. Children validate before the contact write; if the contact commits but a child then fails, the error names the contact's id plus the exact call to finish it, never a silent orphan. A contact with the same email or phone already in this tenant refuses with CONFLICT. NEXT: contact_upsert merges into an existing contact instead of creating a duplicate.