Question: How can you validate the WordPress markup generated by a coding agent?

I have been using the plugin for several days now.

The workflow is smooth: you describe the site, get the pages, work on them, and they improve. My main concern this time is the output markup. WordPress’ Block Editor often finds the markup produced by the agent invalid. When it suggests a fix, instead of correcting it, it ends up breaking it.

Is there a tool or library I can use to validate the produced markup before using it in WordPress' Block Editor?

Thanks,
George J.