I think in this day and age agents no longer need official 3P integrations, they can just use whatever API is already available (and in some cases even the UI).
Still, mcp means you don’t need to figure out the quirks.
Net, I think mcp is extremely good for resource constrained circumstances. I add mcp servers to many of my own applications and it’s an automatic productivity boost.
As a bonus, when I want to automate the integration I literally make my automations use mcp.
The other thing is discoverability, but I’m not sure a simple web search would be significantly less efficient.
My custom MCP server for example handles long running tasks by returning a handle that can be cancelled/queried. This is done in a generic way that all agents can deal with and needed no special instructions.
(Excluding for performance reasons here...)
But yeah of course an agent can usually figure out how to use your API, can just take more time and tokens.