@Han Shih 施學翰 I'm unsure if the schema for it is published but it is a custom format which is kind of a consolidated object of all the relevant properties for an API like authentication settings, revisions, operations, schemas, etc.
Since the YAML files that you use are OpenAPI Files, you could instead export the OpenAPI Spec before/after deployment and use this to keep track of changes.
Also, you might want to explore the CI/CD using ARM Templates doc for the official recommendation for controlled development and deployment.