protocol

MCP protocol of choice: stdin/stdout? WTF, man?

Gregory Golberg projects, self-promotion, silliness, voitta, yak shaving , , , , , , , ,

Let’s talk about MCP. More specifically, let’s talk about using stdin/stdout as a protocol transport layer in the year of our Lord 2025.

Yes, yes—it’s universal. It’s composable. It works “everywhere.” It’s the spiritual successor to Unix pipes, which were cool at the time. The time when my Dad was hitting on my Mom. As an actual transport layer, stdin/stdout is a disaster.

Debugging Is Basically a Crime

Let’s say I want to create an MCP server in Python. Reasonable. Now let’s say I want to debug it. Set a breakpoint. Inspect variables. Use threads. Maybe spin up the LLM in the same process for context. You know, software engineering.

The moment you try to do this, you’re writing a debug driver. Congratulations. You are now:

  • Building a fake client to simulate a streaming LLM
  • Implementing bidirectional IO while praying the LLM doesn’t send surprise newline characters
  • Wrapping things in threads and/or asyncio or multiprocessing or whatnot other total fucking bullshit.

Been there. Twice:

  • Voitta’s Brokkoly: Thought I could run the LLM and the driver in one process. Spent 3 hours implementing queues, got it half-working, and realized I was debugging my own debug tool.
  • Samtyzukki: Round two. Same problem. Ended up with more abstraction layers than a Kafka conference.

Eventually, I just gave up and decided to use SSE (Server-Sent Events). Because you know what’s great about SSE? You can log things. You can see the messages. You can debug. It’s like rediscovering civilization after weeks of wilderness survival with only printf() and trauma.

 stdout Is Sacred, Until It Isn’t

Here’s the other problem. stdout is a shared space. You can’t count on it. Libraries will write to it. Dependencies will write to it. Your logger will write to it. Some genius upstream will write:

print(“INFO: falling back to CPU because the GPU is feeling shy today.”)

Congratulations. You just corrupted your transport. Your parser reads that as malformed JSON or a broken packet or an existential and spiritual crisis.

It’s not a bug. It’s a design decision—and not a good one.

This is the part where I invoke Rob Pike. Sorry. Not sorry.

In Go, to format a date, one doesn’t simply use YYYY-MM-DD. You do Mon Jan 2 15:04:05 MST 2006.

Because, I get it, we all need to get high once in a while. But srsly.

Content assist

Gregory Golberg holding forth , , , , , , , , , , , , , , , ,

It looks like you are researching razors. I think you are about to go off on a yak-shaving endeavor, and I cannot let you do that, Dave.

What I would really like my DWIM
agent to do. That, and to stop calling me Dave.

Being lazy and impatient, I like an idea of an IDE. The ease of things like autocompletion, refactoring, code search, and graphical debugging with evaluation are, for the lack of a better word, are good.

I like Eclipse in particular — force of habit/finger memory; after all, neurons that pray together stay together. Just like all happy families are alike, all emacs users remember the key sequence to GTFO vi (:q!) and all vi users remember the same thing for emacs (C-x C-c n) – so they can get into their favorite editor and not have to “remember”.

So, recently I thought that it would be good for a a particular DSL I am using to have an auto-completion feature (because why should I remember ). So I thought, great, I’ll maybe write an Eclipse plugin for that… Because, hey, I’ve made one before, how bad could it be?

Well, obviously I would only be solving the problem for Eclipse users of the DSL in question. And I have a suspicion I am pretty much the only one in that group. Moreover, even I would like to use some other text editor occasionally, and get the same benefit.

It seems obvious that it should be a separation of concerns, so to speak:

  • Provider-side: A language/platform may expose a service for context-based auto-completion, and
  • Consumer-side: An editor or shell may have a plugin system exposed to take advantage of this.

Then a little gluing is all that is required. (OK, I don’t like the “provider/consumer” terminology, but I cannot come up with anything better — I almost named them “supply-side” and “demand-side” but it evokes too much association with AdTech that it’s even worse).

And indeed, there are already examples of this.

There is a focus on an IDE paradigm of using external programs for building, code completion, and any others sorts of language semantic functionality. Most of MelnormeEclipse infrastructure is UI infrastructure, the core of a concrete IDE’s engine functionality is usually driven by language-specific external programs. (This is not a requirement though — using internal tools is easily supported as well).

  • Atom defines its own API

And so I thought – wouldn’t it be good to standardize on some sort of interaction between the two in a more generic way?

And just as I thought this, I learned that the effort already exists: Language-server protocol by Microsoft.

I actually like it when an idea is validated and someone else is doing the hard work of making an OSS project out of it…