The OpenAPI Specification (OAS) 2.0 defines a root document structure called the Swagger Object. This object has several properties, but only three are mandatory for a specification to be valid. These are swagger, which specifies the OAS version (must be "2.0"); info, which provides metadata about the API; and paths, which defines the available API endpoints and their operations. All other top-level properties listed in the options are optional and provide additional context like the host, base path, or default MIME types.

B. host: This is an optional property that specifies the host (name or IP) serving the API. If omitted, the host is assumed to be the same as where the spec is served.

D. license: The license object is an optional field within the required info object, not a required top-level property of the Swagger Object itself.

F. basePath: This is an optional property that defines the base path relative to the host. If not provided, it defaults to /.

G. produces: This is an optional property that declares a global list of MIME types the API can produce. It can be overridden at the operation level.

H. consumes: This is an optional property that declares a global list of MIME types the API can consume. It can be overridden at the operation level.

1. OpenAPI Initiative

OpenAPI Specification v2.0: The official specification explicitly lists the required fields for the root "Swagger Object". The table in this section indicates that swagger

info

and paths are required.

Source: OpenAPI Specification v2.0

Section: "Swagger Object"

Link: https://github.com/OAI/OpenAPI-Specification/blob/main/versions/2.0.md#swagger-object

2. Google Cloud

Apigee Documentation: Google's documentation on the fundamentals of the OpenAPI specification provides a minimal example that demonstrates the required structure

including only the swagger

info

and paths top-level properties.

Source: Google Cloud Apigee Docs

"What is an OpenAPI specification?"

Link: https://cloud.google.com/apigee/docs/api-platform/fundamentals/what-openapi-specification#a-minimal-openapi-specification