Is there an API exposed for Actions on Google, similar to what Dialogflow offers with their API? The only API-like flow I have found through my research is this webhook flow API, but that only deals with conversation requests, prompts, and responses, which I have already handled.
Ideally I'd like to be able to dynamically create "agents" and their conversation flows without having to use the AoG console, similar to what Amazon offers with Alexa SMAPI.
There's not a full API to do everything that you want end-to-end. Some parts, like Dialogflow and fulfillment, can be automated, but it will still require some manual work in the Actions Console.
I had a conversation with another developer on this subject once. As a workaround, which is admittedly hacky, they decided to use the Puppeteer library to programmatically control a browser instance to fill in fields and click buttons.
That may not necessarily work when the console changes, and isn't a good substitute for an API, but it may work for you.