> So the simpler problem is that your product now becomes merely a tool call for AI agents. That's what users want.

This is a big assumption, and not one I've seen in product testing. Open-ended human language is not a good interface for highly detailed technical work, at least not with the current state of LLMs.

> It's the same reason why API access to SaaS is usually restricted or not available for the users except biggest customers.

I don't... think this is true? Of the top of my head, aside from cloud providers like AWS/GCP/Azure which obviously provide APIs: Salesforce, Hubspot, Jira all provide APIs either alongside basic plans or as a small upsell. Certainly not just for the biggest customers. You're probably thinking of social media where Twitter/Reddit/FB/etc don't really give API access, but those aren't really B2B SaaS products.