MCP is a means of communicating information about externally-defined tools to the “application wrapper” (and your examples of “generic chatbots” are also application wrappers). Well, between the application wrapper and servers; “application wrappers” for LLMs are pretty much the motivating (but not sole) case of MCP Clients.

Without something like MCP, each application wrapper is left do do its own ad hoc wrappers for external tools (tools internal to the wrapper don’t use MCP.) With MCP, it just integrates an MCP client library, and then it can use any tool, resource, or prompt provided by any MCP server available to it.