It took me some time to wrap my head around why WebMCP even exists. I was thinking that regular MCP + SSE/Websockets could cover almost all of the uses cases.

One interesting use case for WebMCP is cross-site activities that a browser agent might take. If the data-flow in question involves a heterogeneous set of websites.

This feels like a lifeline for incumbent web SaaS more than anything. Future apps can be architected in ways that do not require WebMCP but massive apps like Salesforce or Workday can't really abandon the decades of accidental business logic embedded in the Web UI flows that make up their project. While those same flows could be data-driven, slapping a WebMCP facade on top of them is just more practical. Instead of forcing incumbents to create an AI-native MCP where they are first class citizens, it is easier to let them sprinkle browser affordances throughout their human-centric front-end and offload the work to the agent.

But for my own part, since I am developing from scratch without that legacy need, I actually think relying on WebMCP might be an anti-pattern. It might be useful for the cross-site use case and it might be useful for reducing latency for purely UI activities (e.g. "filter this list" where all the data is already on the client), but in general my feeling is it is better to have a robust MCP interface for agents.