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Comment by rco8786 | Hacker News Reader

> when LLMs can just connect to the existing API endpoint

The primary differentiator is that MCP includes endpoint discovery. You tell the LLM about the general location of the MCP tool, and it can figure out what capabilities that tool offers immediately. And when the tool updates, the LLM instantly re-learns the updated capability.

The rest of it is needlessly complicated (IMO) and could just be a bog standard HTTP API. And this is what every MCP server I've encountered so far actually does, I haven't seen anyone use the various SSE functionality and whatnot.

MCP v.01 (current) is both a step in the right direction (capability discovery) and an awkward misstep on what should have been the easy part (the API structure itself)

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How is this different than just giving the LLM an OpenAI spec in the prompt? Does it somehow get around the huge amount of input tokens that would require?

Technically it's not really much different from just giving the LLM an OpenAPI spec.

The actual thing that's different is that an OpenAPI spec is meant to be an exhaustive list of every endpoint and every parameter you could ever use. Whereas an MCP server, as a proxy to an API, tends to offer a curated set of tools and might even compose multiple API calls into a single tool.

It's a farce, though. We're told these LLMs can already perform our jobs, so why should they need something curated? A human developer often gets given a dump of information (or nothing at all), and has to figure out what works and what is important.

You should try and untangle what you read online about LLMs from the actual technical discussion that's taking place here.

Everyone in this thread is aware that LLMs aren't performing our jobs.

Because again, discoverability is baked into the protocol. OpenAI specs are great, but they are: optional, change over time, and have a very different target use case.

MCP discoverability is designed to be ingested by an LLM, rather than used to implement an API client like OAI specs. MCP tools describe themselves to the LLM in terms of what they can do, rather than what their API contract is.

It also removes the responsibility of having to inject the correct version of the spec into the prompt from the user, and moves it into the protocol.

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