All of these things are perfectly possible with a plain REST API with an Open API spec and using some standard auth options, and an AI client that implements a reasonable “make api request tool” (just like the AI clients implement MCP today).

I think the real value of MCP is that it allowed companies to say “we’re doing AI!” When they built an MCP server. Just saying “use our api” was a lot less exciting.

Giving it a different name probably also helped cut through politics at companies where non-technical people didn’t want to open up user data with an API, but they did want to do AI.

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simonw 5 hours ago | parent | next [-]

Hah, I made that same point last December: https://simonwillison.net/2025/Dec/31/the-year-in-llms/#the-...

> For a while it also felt like MCP was a convenient answer for companies that were under pressure to have “an AI strategy” but didn’t really know how to do that.

I've since come back to MCPs, because I want to build my own agents without first having to solve the problem of effectively sandboxing Bash.

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mikeocool 5 hours ago | parent | next [-]

Yeah, from a design perspective MCP upsets me, because it’s a poorly designed standard and creating a good one could have been much easier.

But you’re right, since clients don’t have a nicely sandboxed “make api request” tool, it’s basically the way to go for a lot of use cases.

	▲	rsalus 7 minutes ago \| parent [-]
		I think the new 07-28 spec is quite decent

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agentdev001 4 hours ago | parent | prev [-]

"without first having to solve the problem of effectively sandboxing Bash"

Hopefully this is easier as time goes on. Of course- also policy on the egress

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what-the-grump 3 hours ago | parent | prev | next [-]

Pretty much, MCP is still a bad idea.

LLMs perform significantly better and faster when you strap them to plain old apis/and an open api spec with a search tool.

My current MCP design is… grab a fastapi spec shove it into fastmcp, shallow wrapper, search tool for the full schema.

Oh boy so exciting I just wrapped an api spec for no reason and have to host infra for the translation layer. If only we invented api gateways.

But I am Mr. AI now.

	▲	isbvhodnvemrwvn 2 hours ago \| parent [-]
		How do you handle credentials safely?

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rgbrgb 5 hours ago | parent | prev [-]

it's mostly true but the mcp also installs the knowledge of that REST API in a standard way so that a user can ask "what's projected revenue this month?" and it'll know how to hit your company brain and answer