I'm not sure what you mean? LLMs can only be interacted with using prompting. Even the tool call response from OpenAPI is them just wrapping the prompt on their side of the API with another prompt.
So everything else is just adding behavior around it.
MCP is a way to add behavior around LLM prompting for user convenience.
It's nice to have an open standard though. In that sense it's pretty awesome.
But MCP isn't just tools, you can expose prompt templates and context resources as well.
All the skills that don't have an added dependency on a local script could just be an MCP resource.