The OpenAPI 2.0 specifications are deprecated and are not maintained.
"IBM provides these older versions of the Watson APIs in Swagger version 2.0 format (the "Swagger APIs"). You may use the Swagger APIs to provide capabilities or integrations that leverage the older versions of the APIs. The Swagger APIs are provided as-is, and IBM does not make any commitments about the quality, reliability, availability, or ability of the Swagger APIs to meet your needs.
See OpenAPI 3.0 Specifications.