Beta: this endpoint is still in active development; payload shape and validation rules may change.

Creates a document type in the caller's organization. The name is required; everything else is optional. externalId must be unique per organization. validationSettings is a JSON-encoded string whose only recognised keys today are validFor and issuedAfter (each { "value": number, "unit": "DAYS"|"MONTHS"|"YEARS" }).

Once created, reference the returned id from a Campaign DOCUMENT question via documentItems: [{ documentTypeId }]. The server populates a readable documentTypeName copy on each reference so the Campaign payload is greppable without a join. See POST /v1/campaigns for the per-question shape.