Where is the source of AWS services?

What is the source from which AWS APIs and language bindings are generated from?

Published: Saturday, Nov 27, 2021 Last modified: Saturday, Jan 1, 2022

When boto updates: https://github.com/boto/botocore/commit/d9d692f7a350417480f8eb9592d8b0c936b6825a

Or the AWS GO SDK updates: https://github.com/aws/aws-sdk-go-v2/pull/1507

Where are the original models?

Is it the CloudFormation resource provider schemas?

After a frantic search it would appear to be an XML based Coral is how AWS sources a service.

With the future to be https://awslabs.github.io/smithy/ ?