No, MCP does not include any concept of UI (yet). Tool results are usually text only, although there is also the abstraction of an Image (which can be displayed as clients as decide to, e.g. inline).
So no application code needs to be changed because no application code exists.
Isn't that like saying you don't need to modify application code with an REST API if your "application" is just a list of instructions on how to use wget/bash to accomplish the task?
Isn't that like saying you don't need to modify application code with an REST API if your "application" is just a list of instructions on how to use wget/bash to accomplish the task?