Kind of. The AWS CLI uses an Amazon internal modeling format used to define services that's based on another Amazon internal modeling format that has been in use for about 15 years (and it's based on another internal model etc..). Smithy is basically the open source v2 of both, but with a public spec and tooling. Eventually all the AWS SDKs and the AWS CLI will adopt Smithy. (I work on the AWS SDKs and created Smithy)