You're thinking like a SW engineer. Instead, think like someone who just happens to know a bit of programming. MCP is much, much easier than tool calling, I think.

As an example, I wrote a function in Python that, given a query string, executes a command line tool and returns the output. To make it an MCP server, I simply added type annotations to the function definition, and wrote a nice docstring, and added a decorator.

That's it. And now it works with all providers and all tools that support MCP. No REST APIs, etc needed. Not tied to a particular agentic tool.

Every time I've written a tool, I've ended up with "Wow, was it really that simple?"

As for security: If you write your own tool, the security implications are the same.