This is coming late as skills have largely replaced MCP. Now your site can just host a SKILL.md to tell agents how to use the site.
The purpose of this appears to be for sites that cannot be controlled via prompt instructions alone.
I do like agent skills, but I’m really not convinced by the hype that they make MCP redundant.
Skills are great for static stuff but they kinda fall apart when the agent needs to interact with live state. WebMCP actually fills a real gap there imo.
It's not meant to describe how to use the site, it should / can replace the need for playwright and DOM inspection / manipulation entirely.
Think of it like an "IDE actions". Done right, there's no need to ever use the GUI.
As opposed to just being documentation for how to use the IDE with desktop automation software.