In the case of MCP, no application code is modified. You first ship the application and then functionality is added. Using plain APIs, it's the other way around. That's the difference.
If my application performs some function dependant on data from an API(e.x. showing tax information, letting a user input tax information, and performing tax calculations and autocomplete), how do I extend that UI easier with MCP than with an HTTP REST API.
Even with MCP I need to update my application code to add UI elements(inputs, outputs) for a user to interact with this new functionality, no?
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?