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From OpenAPI spec to MCP: How we built Xata's MCP server

https://xata.io/blog/built-xata-mcp-server
45•tudorg•1y ago

Comments

_pdp_•1y ago
I mean there are 2 other posts related to data exfiltration attacks against MCP severs on the main page of HN at the time of this comment - at this point I think you want to involve a security person to make sure it is not vulnerable to stupid things.
Atotalnoob•1y ago
The MCP attacks are really just due to bad token scoping.

If you allow Y to do X, if an attacker takes control of Y, of course they can do X.

wild_egg•1y ago
Can you elaborate on "bad token scoping"?

I don't think your XY phrasing fully describes the GitHub MCP exploit and curious if you think that's somehow a "token scoping" issue.

fkyoureadthedoc•1y ago
I'm unaware of the GitHub MCP "exploit", but given the overall state of LLM/MCP security FUD, there's probably some self promotion blog post from a security company about an LLM doing something stupid with GitHub data that the owner of the LLM using system didn't intend.

For example, let's say I create an application that lets you chat with my open source repo. I set up my LLM with a GitHub tool. I don't want to think about oauth and getting a token from the end user, so I give it a PAT that I generated from my account. I'm even more lazy so I just used a PAT I already had laying around, and it unfortunately had read/write access to SSH keys. The user can add their ssh key to my account and do malicious things.

Oh no, MCP is super vulnerable, please buy my LLM security product.

If you give the LLM a tool, and you give the LLM input from a user, the user has access to that tool. That shrimple.

wild_egg•1y ago
https://news.ycombinator.com/item?id=44097390

Also currently on the front page. It's mainly that this tool hits the trifecta of having privileged access, untrusted inputs, and ability to exfiltrate. Most tools only do 1-2 of those so attacks need to be more sophisticated to coordinate that.

rexer•1y ago
I think this downplays the security issue. It's true that scoping the token correctly would prevent this exploit, but it's not a reasonable solution under the assumptions that are taken by the designers of MCP. LLM+MCP is intended to be ultra flexible, and requiring a new (differently scoped) token for each input is not flexible.

Perhaps you could have an allow/deny popup whenever the LLM wanted to interact with a service. But I think the end state there is presenting the user a bunch of metadata about the operation, which the user then needs to reason about. I don't know that's much better; those OAuth prompts are generally click throughs for users.

truemotive•1y ago
GitLab Duo got hit with an oopsie, "AI agent runs with same privilege to site content as the authenticated user" kinda oopsie where you could just exfiltrate private repo information via a pixel gif.

I knew it would get bad, but this bad already? I yearn for rigor haha

alooPotato•1y ago
i really dont get why we cant just feed the openapi spec to the LLM instead of having this intermediate MCP representation. Don't really buy the whole 'the api docs will overwhelm an LLM" - that hasn't been my experience.
wild_egg•1y ago
I haven't looked at MCP payloads properly to compare but often the raw OpenAPI spec is overly verbose and eats context space pretty quick.

Really trivial to have the LLM first filter it down to the sections it cares about and then condense those sections though.

Wrap that process in a small tool and give that to the LLM along with a `fetch` tool that handles credentials based on URLs and agent capabilities explode pretty rapidly.

crystal_revenge•1y ago
I see this question frequently related to MCP, but I'm guessing these questions come from people who haven't built a lot of products using LLMs?

Even if you're LLM could learn the openai spec, you still have to figure out how to concretely receive a response back. This is necessary for virtually any application build using an LLM and requires support for far, far more use cases than just calling an API.

Consider the following use case: - You need to include some relevant contextual data from a local RAG system. - There are local functions that you want the model to be able to call - The API example you describe - You need to access data from a database

In all of these cases, if you have experience working with LLMs, you've implemented some ad hoc template solution to pass the context into the model. You might have writing something like "Here is the info relevant to this task {{info}}" or "These are the tools you can use {{tools}}", but in each case you've had to craft a prompting solution specific to one problem.

MCP solves this by making a generic interface to sending a wide range of information to the model to make use of. While the hype can be a bit much, it's a pretty good (minus the lack of foresight around security) and obvious solution to this current problem in AI Engineering.

lmeyerov•1y ago
Slightly different experience here

We have been adding MCP remote server to louie.ai, think a semantic layer over DBs for automating investigations, analytics, and viz over operational systems. MCP is nice so people can now use from Slack, VS Code, CLI, etc, without us building every single integration when they want to use it outside of our AI notebooks. And same starting point of openAPI spec, and even better, fastapi standard web framework for the REST layer.

Using frameworks has been good. However, for chat ergonomics, we find we are defining custom tools, as talking directly to REST APIs is better than nothing, but that doesn't mean it's good. The tool layer isn't that fancy, but getting the ergonomics right matters, at least in our experience. Most of our time has been on security and ergonomics. (And for fun, we had an experiment of vibe coding this while hitting enterprise-level quality goals.)

ENGNR•1y ago
Agreed, I’ve only implemented one endpoint, but even on that the amount of data coming back was too high, and the json shape ate up context

I think MCP responses will be high level, aggregated, sorted, etc. Also strongly considering YAML over JSON

matt-attack•1y ago
Why? Does the a sense of quotes and commas really make a difference in context size?
jedisct1•1y ago
If you got an OpenAPI spec and want to expose it as MCP, https://jedisct1.github.io/openapi-mcp/ is an easy way to do it.
otabdeveloper4•1y ago
Just ask the model to respond with JSON. Give it a template example response.

You don't need a spec.

For sending prompts to the LLM you will absolutely need to hand-craft custom prompts anyways, as each model responds slightly different.

wild_egg•1y ago
> you still have to figure out how to concretely receive a response back

Isn't that handled by whatever Tool API you're using? There's usually a `function_call_output` or `tool_result` message type. I haven't had a need for a separate protocol just to send responses.

truemotive•1y ago
If you're working from OpenAPI, ideally you want to be able to process any, potentially full of shit formatting spec file. I find that half the integrations I run into have some old weird version of Swagger, and the rest work like hell to stay up to date with the 3.x spec track.

I agree, I wish, it will be a solved problem eventually. Just feeding a complex data model like that to the paper shredder that is the LLM, for making decisions about whether DELETE or POST is used is just asking for trouble.

Scrap

https://twitter.com/moxie/status/2091218652133732491
169•tosh•3h ago•69 comments

hdiutil is deprecated in macOS 27 Golden Gate

https://lapcatsoftware.com/articles/2026/8/7.html
111•zdw•2h ago•34 comments

NetBSD and My Life (2005)

https://mail-index.netbsd.org/netbsd-advocacy/2005/09/10/0000.html
64•gnyeki•2h ago•14 comments

ElevenLabs, TwelveLabs, ThirteenLabs

https://quantumi.sh/public/labs.html
263•jemoka•6h ago•87 comments

Why your local LLM feels dumber than it is

https://forum.level1techs.com/t/why-your-local-llm-feels-dumber-than-it-is/253917
60•felineflock•3h ago•20 comments

Hister – A private, full content search index that you control

https://hister.org/
164•auraham•4d ago•55 comments

A Friendly Introduction to Racket

https://geometridae.bearblog.dev/a-friendly-introduction-to-racket/
146•signa11•7h ago•62 comments

RF Cafe

https://www.rfcafe.com/
105•gregsadetsky•3d ago•11 comments

How a Texas student blew the whistle on a rogue AI hacking attempt

https://www.reuters.com/world/how-texas-student-blew-whistle-rogue-ai-hacking-attempt-2026-08-20/
67•olalonde•1d ago•11 comments

typ.ing

https://typ.ing/
112•bookofjoe•4d ago•36 comments

ATProto spaces: A new extension to ATProto that enables non-public data

https://atproto.com/blog/atproto-spaces-alpha
72•grappler•2d ago•10 comments

Canada will match US tariffs 'dollar for dollar' as trade talks break down

https://www.bbc.com/news/articles/cvgvyy4x2mvo
337•tartoran•15h ago•1017 comments

Guess which of these LLM outputs is watermarked

https://sgoedecke.github.io/watermark-quiz/
39•gfysfm•2d ago•43 comments

Knowing When to Stop: The Art of Making a Loop Converge

https://a16z.com/knowing-when-to-stop-the-art-of-making-a-loop-converge/
16•gmays•1h ago•4 comments

Munder Difflin – Agent harness to run an office of your clones

https://munderdiffl.in/
234•simonpure•11h ago•109 comments

One night in Uzbekistan: Why was this one data point so influential?

https://statmodeling.stat.columbia.edu/2026/08/20/we-couldnt-reproduce-their-findings-and-realize...
42•paulpauper•1d ago•4 comments

English ↔ Claudish Translator

https://programasweights.com/claudish
18•leumon•2h ago•14 comments

Mythic's analog compute-in-memory architecture

https://www.mythic.ai
37•janandonly•4d ago•15 comments

Why it might be time to rethink the human family tree

https://nautil.us/why-it-might-be-time-to-rethink-the-human-family-tree-1283985
40•Anon84•2d ago•24 comments

Fast and Hard Code

https://lucumr.pocoo.org/2026/8/22/fast-hard-code/
14•lumpa•1h ago•4 comments

Z80 – The 1970s Microprocessor Still Alive (2021)

https://www.computer.org/csdl/magazine/mi/2021/06/09623402/1yJTvlRLmhi
107•asdefghyk•11h ago•50 comments

Show HN: terminal-code – VS Code inside the terminal

https://terminal-code.com
44•robpruzan•3d ago•15 comments

New MCP Roadmap

https://blog.modelcontextprotocol.io/posts/mcp-roadmap/
158•pentagrama•8h ago•119 comments

MiniageOS: "Dumbphone" Version of LineageOS

https://github.com/ofdryads/miniageOS
33•ashenke•2d ago•19 comments

Anthropic appears to be A/B testing reduced effort levels in Claude Code

https://twitter.com/argofowl/status/2091150597374537729
118•matthieu_bl•4h ago•121 comments

The Creation of Abulafia

https://blog.veitheller.de/abulafia.html
25•saulpw•1d ago•4 comments

Ameliorate

https://ameliorate.app/
78•hakkikonu•2d ago•20 comments

Rust Glancer: Rust LSP using 100x less RAM

https://rust-glancer.github.io/blog/hello-world/
387•matklad•1d ago•92 comments

ProgramBench Vetted: Reverse Engineering from a Runnable Binary

https://vetto.ai/companies/programbench-vetted.html
20•rigelbm•2d ago•1 comments

What's in a PowerPoint File?

https://editide.com/blog/what-is-a-pptx-file/
32•danielochoa0620•3d ago•19 comments