MsgPack (LsMsgPack)

Name: MsgPack (LsMsgPack)
Author: mlsomers

by mlsomersversion 2026.11.6.1i★ –iRuns on your computer

Registry nameio.github.mlsomers/lsmsgpack

Install

Overview

Description from the maker (original English)

Decodes MsgPack (LsMsgPack schemas, type ids) as text and reads it from variables while debugging.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiNot measured yet★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs on your computer
Transport: stdio
Category: Developer tools

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on your computer with your user’s permissions (files, network, apps).
The registry lists no key to fill in.

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Open Claude Desktop → Settings → Developer → Edit Config, and paste this into claude_desktop_config.json

{
  "mcpServers": {
    "lsmsgpack": {
      "command": "dnx",
      "args": [
        "LsMsgPack.Mcp",
        "--yes"
      ]
    }
  }
}

Run this in your terminal

claude mcp add lsmsgpack -- dnx LsMsgPack.Mcp --yes

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "lsmsgpack": {
      "command": "dnx",
      "args": [
        "LsMsgPack.Mcp",
        "--yes"
      ]
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "lsmsgpack": {
      "type": "stdio",
      "command": "dnx",
      "args": [
        "LsMsgPack.Mcp",
        "--yes"
      ]
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

This one runs on your computer, and ChatGPT can only connect to servers on the internet. Pick another app.

Your choice stays on this device in a cookie; no account needed.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Runs on your computer; the tool list appears in your AI app after you install it.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 6, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account mlsomers, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
– Not applicable
Endpoint responds
This one runs on your computer; there is no internet endpoint
– Not applicable
Sign-in with OAuth
Runs on your computer and uses local settings instead
… Not checked yet
No hidden instructions in tool descriptions
Runs on your computer; we can only read tool lists from internet endpoints

Compared with others in Developer toolsi

More stars than 0% of the other 1387 servers in this category
Published to the registry more recently than 99% of the other 1387 servers in this category
Basic checks equal to or better than 100% of the other 1387 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is MsgPack (LsMsgPack) safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs on your computer. Your AI app starts it when needed, and data does not pass through the maker’s servers (unless it calls an online service itself).

Is it still maintained?

The GitHub repo last changed –, and the latest version (2026.11.6.1) reached the registry today.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. You also need .NET on your computer.

What can I use instead?

In the same category: GitHub, Desktop Commander, Cloudflare MCP

Alternatives

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Reading a card:★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

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README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

LsMsgPack MCP server

MsgPack for AI agents. An MCP server and a command line tool that decode MsgPack data into text an AI (or a person in a terminal) can read, and that read the bytes of a variable of a program paused in the debugger of VS Code or Visual Studio.

Language models read text, not bytes. Hex or base64 costs several tokens per byte, and decoding it by hand is slow and error-prone. Some data can't be decoded from the bytes at all: LsMsgPack's indexed schema writes property names as indexes, and a schema reference holds only the 16-byte id of the schema. This tool decodes the data with the LsMsgPack library itself (the code of MsgPack Explorer) and writes it as JSON with comments:

MsgPack "doc1" 247 bytes from payload (byte[], Launch Api).

Structure: indexed schema (inline, 3 types) followed by the body No errors, 0 warnings or comments. Schema (inline): type ids and property ids in the body are indexes into these lists. #0 Invoice: Id, Customer, Billing, Lines, Date, Reference, Tags #1 Address: Street, Number, City #2 Line: Product, Quantity, Price

Objects (JSON with // comments: a type name comes from a type id, a name with ~ is inferred from the schema; dictionary keys that are not strings are not quoted): { // Invoice~ "Id": 1234, "Customer": "Alice", "Billing": { "Street": "Main street", "Number": 12, "City": "Amsterdam" }, // Address~ "Lines": [ // 2 items { "Product": "Apples", "Quantity": 3, "Price": 1.25 }, // Line~, Price: decimal { "Product": "Pears", "Quantity": 2, "Price": 0.99 } // Line~, Price: decimal ], "Date": "2026-10-05T12:30:00Z", // timestamp "Reference": "5bad8f0fcbd99f46a16570867728950e", // bin, 16 bytes, as Guid 0f8fad5b-d9cb-469f-a165-70867728950e "Tags": ["fruit", "fresh"] // 2 items }

It reads any MsgPack, not only data written by LsMsgPack. Errors come with their offset, and the values read after an error are marked.

Install

Requires the .NET runtime 8 or later.

dotnet tool install -g LsMsgPack.Mcp      # the command is lsmsgpack-mcp

From source: dotnet publish LsMsgPackMcpServer -c Release -o , then run dotnet /LsMsgPackMcp.dll in place of lsmsgpack-mcp.

Add it to your agent

Client	How
VS Code (Copilot agent mode)	Nothing to do with the MsgPack Explorer extension: it registers the server "MsgPack (LsMsgPack)".
Claude Code	`claude mcp add lsmsgpack -- lsmsgpack-mcp`
Visual Studio 2022 (17.14+)	`%USERPROFILE%\.mcp.json` (or `.mcp.json` next to the solution): `{ "servers": { "lsmsgpack": { "type": "stdio", "command": "lsmsgpack-mcp" } } }`
Claude Desktop, Cursor, Windsurf...	`{ "mcpServers": { "lsmsgpack": { "command": "lsmsgpack-mcp" } } }`

In VS Code, MsgPack: Copy MCP Server Configuration... copies these: for the tool when it is installed, otherwise for the server that comes with the extension (its path has the extension's version in it, so copy it again after an update).

Tools

Tool	What it does
`msgpack_debug_status`	The IDEs with the MsgPack extension, their debug sessions, and where the program is paused.
`msgpack_debug_locals`	The variables of the paused stack frame with their types. The ones that can hold bytes are marked.
`msgpack_debug_read`	Reads the bytes of an expression in the paused program and decodes them. Reads `byte[]`, streams (seekable ones go back to their position), `Memory` , `List` , `HttpContent` and base64 or hex strings. In VS Code also JavaScript `Uint8Array`/`Buffer` and Python `bytes`. `schemaStore` reads the schema from the program's `SchemaStore` when the payload refers to one. `saveTo` also writes the bytes to a file.
`msgpack_decode`	Decodes `data` (hex, base64 or byte values), a `file`, or a `doc` decoded before. `schemas` takes a `SchemaStore.Export` (or one schema) for schema references.
`msgpack_read_as_class`	Reads the data into a class of a compiled .NET assembly (`assembly`: the `.dll` of the build output, `type`: the class) and reports what doesn't match: properties the class doesn't have (with "did you mean"), values that don't convert, classes without a schema entry, type ids that aren't found, with the paths of the objects (reporting differences). Also shows the object that was read. The assembly is loaded in a separate process: it runs the class's constructors and setters.
`msgpack_explain_offset`	What the byte at an offset is: the items holding it, the object member, the header and content bytes, and the bytes around it.
`msgpack_search`	The items holding a text or a value, with offsets and object paths.

Every decoded payload gets a document id (doc1, doc2...) for follow-up calls. The output can be narrowed and switched with these options:

view: objects (default), items (the MsgPack encodings with offsets) or both.
path (e.g. Lines[2]), from/to (a byte range), maxNodes, maxString.
offsets adds the offset of every value. issues takes errors, all or none.
endian and continueOnError (on by default).

Debugging

The MsgPack extensions of VS Code (MsgPack Explorer) and Visual Studio (MsgPack Debugger Extension) listen on 127.0.0.1. They write a lock file with their port and a random token to ~/.lsmsgpack/ide (%USERPROFILE%\.lsmsgpack\ide). The MCP server uses the IDE that started it, otherwise the one whose workspace holds its working directory (ide picks one when several run).

By default only variable and member paths are read (buffer, this._payload, response.Content, items[2].Data), no method calls. The IDE setting can allow any expression: lsmsgpack.mcp.allowAnyExpression in VS Code (user settings only), Tools > Options > MsgPack Explorer in Visual Studio.
A stream that can't seek is consumed by reading it, so the IDE asks the user first.
The IDE settings can turn the bridge off: lsmsgpack.mcp.enabled in VS Code, and the same options page in Visual Studio.

Command line

lsmsgpack-mcp decode payload.msgpack                # the objects

lsmsgpack-mcp decode payload.msgpack --view items # the items with offsets and encodings lsmsgpack-mcp decode --data "82 a4 4e 61 6d 65 ..." # bytes as text lsmsgpack-mcp explain payload.msgpack 0x7b # what the byte at 0x7b is lsmsgpack-mcp search payload.msgpack Amsterdam lsmsgpack-mcp read-as payload.msgpack --assembly bin/Debug/net8.0/MyApp.dll --type Order # what doesn't match the class lsmsgpack-mcp debug status | debug locals | debug read

lsmsgpack-mcp --help lists the options. Without arguments it runs the MCP server on stdin/stdout.

More: docs/Mcp.md.

MsgPack (LsMsgPack)

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Developer toolsi

Common questions

Alternatives

GitHub

Desktop Commander

Cloudflare MCP

README from the maker

LsMsgPack MCP server

Install

Add it to your agent

Tools

Debugging

Command line