MCP is just as worse version of the above allowing lots of data exfiltration and manipulation by the LLM.
The classic "API key" flow requires you to go to the resource site, generate a key, copy it, then paste it where you want it to go.
Oauth automates this. It's like "give me an API key" on demand.
You could do the same with a CLI tool but it's more of a hassle to set up.