OSCAL Tools
NIST has developed and maintains open source commodity tooling, applications frameworks and libraries to support working with OSCAL see NIST OSCAL Tools web page. Additional open source and commercial tools are referenced on that NIST OSCAL tools web page.
The FedRAMP automation team is working to add Metaschema-based validation mechanisms to the OSCAL-CLI tool to enable it to support both core NIST OSCAL constraint validation and additional FedRAMP constraints and requirements.