Everything wrong with MCP

Posted by sshh12 4/13/2025

516 points | 223 commentspage 2

madrox 4/14/2025|

Nothing the author said is wrong, but I don’t know how much it matters or if it would’ve been better if it handled all this out of the gate. I think if MCP were more complicated no one would’ve adopted it.

Being pretty close to OAuth 1.0 and the group that shaped it I’ve seen how new standards emerge, and I think it’s been so long since new standards mattered that people forgot how they happen.

I was one of the first people to criticize MCP when it launched (my comment on the HN announcement specifically mentioned auth) but I respect the groundswell of support it got, and at the end of the day the standard that matters is the one people follow, even if it isn’t the best.

rcarmo 4/14/2025||

There is one thing I pointed out in https://taoofmac.com/space/notes/2025/03/22/1900 and seems to be missing from the article:

"... MCP tends to crowd the model context with too many options. There doesn’t seem to be a clear way to set priorities or a set of good examples to expose MCP server metadata–so your model API calls will just pack all the stuff an MCP server can do and shove it into the context, which is both wasteful of tokens and leads to erratic behavior from models."

sshh12 4/14/2025|

It's in there briefly in the llm limitations section.

behnamoh 4/14/2025||

Yeah, I don't feel comfortable downloading tiny server programs from random devs on the internet to give my LLM client apps extra "tools". I can LuLu or LittleSnitch regular apps but not these ones.

ezyang 4/14/2025||

I quite liked this article, actually, and I'm quite an MCP stan. These all seem like legitimate problems that the burgeoning ecosystem needs to figure out. Some of them will be logically solved inside the MCP spec, but I also think some won't.

lacker 4/14/2025||

Is anyone successfully using Claude Code along with MCP?

I feel like I hear very many stories of some company integrating with MCP, many fewer stories from users about how it helps them.

zoogeny 4/14/2025|

I've heard the opposite, stories from users that MCP has been a flop. One of my acquaintances works in marketing and is a heavy LLM user. He got swept up in the hype of MCPs and tried a bunch of them out. He was expressing his disappointment and frustration.

It is a drawback of hype and early adoption. I think highly technical users can get value out of it for now and can keep their expectations in line. If I am building my own MCP server and it is a bit flaky, I manage that responsibility myself. If I am wiring up a MCP server that makes some claims of automating some workflow and it doesn't work, then I negatively associate that with the very idea of MCP.

angusturner 4/14/2025||

I have been developing with MCP for a few weeks now, making some small python and javascript servers to integrate with Claude Desktop.

I am yet to see a use case that wouldn't be better served with an HTTP API. I understand the need to standardize some conventions around this, but at the heart of it, all "tool" use boils down to: 1. an API endpoint to expose capabilities / report the API schema 2. other endpoints ("tools") to expose functionality

Want state? ("resources") - put a database or some random in-memory data structure behind an API endpoint. Want "prompts"? This is just a special case of a tool.

Fundamentally (like most everyone else experimenting with this tech), I need an API that returns some text and maybe images. So why did I just lose two days trying to debug the Python MCP SDK, and the fact that its stdio transport can't send more than a few KB without crashing the server?

If only there was a stateless way to communicate data between a client and a server, that could easily recover from and handle errors...

crabmusket 4/14/2025|

APIs aren't self describing by default, but it feels like a missed opportunity for REST and HATEOAS proponents to show the value in those approaches. I've always said REST is for human clients, and LLMs seem like they should be human enough for this kind of thing.

Xelynega 4/15/2025|||

MCP is not self describing by default either.

I can implement a tool and not add it to the definitions, much like you can implement an API endpoint and not add it to the spec.

This is a documentation/code synchronization problem that is solved the same way for both MCP and REST, generate documentation from code.

ikiris 4/14/2025|||

Rest is for people who thought xml was a good idea.

crabmusket 4/14/2025||

XML was a good idea ¯\_(ツ)_/¯

krige 4/14/2025||

Does it at least say "END OF LINE" and banish wannabe hackers to the game grid?

cynicalpeace 4/14/2025||

MCP has a LangChain smell.

Doesn't solve a pressing problem that can't be solved via a few lines of code.

Overly abstract.

Tons of articles trying to explain its advantages, yet all somehow fail.

jascha_eng 4/14/2025||

Something that I struggle with in regards to MCP and no-ones really touches on: We don't even know if this "general" Chatbot paradigm will persist. So far I got the feeling that we end up building specialized apps for specialized use-cases (e.g. cursor or claude code for coding) These then bring their own set of tools (for file writing, reading, running bash commands, etc.) and don't really need MCP (except for very niche use-cases maybe).

I don't really see the point yet where LLMs become so good that I throw my specialized LLM tools out and do everything in one claude desktop window. It simply doesn't work generic enough.

Also... if you end up building something custom, you end up having to reimplement the tool calling again anyways. MCP really is just for the user facing chat agents, which is just one section of AI applications. It's not as generically applicable as implied.

zoogeny 4/14/2025||

Interestingly, my criticism is exactly the opposite of yours. I think as LLMs become more and more capable (and crucially multi-modal) we will need the external tools less and less.

For example, why would I want an MCP that can drive Photoshop on my behalf? Like I say to the LLM "remove this person from the photo" and it opens Photoshop, uses the magic wand select tool, etc. That is silly in my mind. I want to say "remove this person" and the LLM sends me a perfect image with the person gone.

I extend that idea for just about any purpose. "Edit this video in such and such a way". "Change this audio in such and such a way". "Update this 3d model in such and such a way". No tool needed at all.

And that will lead to more multi-modal input. Like, if I could "mark up" a document with pen marks, or an image. I want tools that are a bit better than language for directing the attention of the model towards the goals I want them to achieve. Those will be less "I am typing text into a chat interface with bubbles" but the overall conversational approach stays intact.

otabdeveloper4 4/15/2025|||

> We don't even know if this "general" Chatbot paradigm will persist

It won't. These startups are selling the sci-fi robot assistant dream; think Tony Stark or Captain Picard or whatever. Once the novelty wears off nobody is going to pay big bucks for what is essentially just childhood nostalgia.

For everything else you'd want hyperspecialized language manipulation tools.

fragmede 4/14/2025||

If you have a better idea you could get millions in VC funding to pursue that. Chat is where it's at. It's fine to think that it's not gonna be the be-all and end-all of AI, but it's pretty fundamentally how we interact with each other, so I don't see it going away any time soon. There's also a thing as being too generic. So really they just hit this sweet spot.

skydhash 4/14/2025||

> If you have a better idea you could get millions in VC funding to pursue that.

I would like to see:

- Some Smalltalk-like IWE (Integrated Work Environment), creating prompt snippets and chaining them together.

- A spreadsheet like environment. Prompt's result are always tables and you have the usual cell reference available.

fragmede 4/15/2025||

Fascinating idea. Though I will note that prompt results aren't usually tables when I ask ChatGPT to ask me questions to help me figure out where I personally stand on, say, hot button political issues.

skydhash 4/15/2025||

That should be an Access database.

lbeurerkellner 4/14/2025|

I think what is not to be overlooked in these discussions, is the user base of MCP.

In my experience, many less-technical folks started using MCP, and that makes security issues all the more relevant. This audience often lacks intuition around security best-practices. So it’s definitely important to raise awareness around this.

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