MCP Slim Guard

Name: MCP Slim Guard
Author: lennney

by lennneyversion 0.1.1-alpha.1i★ –iRuns on your computer

Registry nameio.github.lennney/mcp-slim-guard

Install

Overview

Description from the maker (original English)

76% fewer MCP tokens in our standard benchmark. Same upstream call. Exact recovery.

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
UsageiVery new↓ 52/wk · ★ –

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: Other

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.

You need

npmNode.js installed (for the npx command)

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": {
    "slim-guard": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-slim-guard"
      ]
    }
  }
}

Run this in your terminal

claude mcp add slim-guard -- npx -y mcp-slim-guard

Open in Cursor

Or copy the settings yourself

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

{
  "mcpServers": {
    "slim-guard": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-slim-guard"
      ]
    }
  }
}

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": {
    "slim-guard": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "mcp-slim-guard"
      ]
    }
  }
}

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 9, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account lennney, 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 Otheri

More stars than 0% of the other 18697 servers in this category
Published to the registry more recently than 17% of the other 18697 servers in this category
Basic checks equal to or better than 100% of the other 18697 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 MCP Slim Guard 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 (0.1.1-alpha.1) reached the registry 3 months ago.

Which apps can use it?

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

What can I use instead?

In the same category: Spec Driven Development, Remote Desktop Commander, phylokit-mcp

Alternatives

Servers in the same category from other makers, sorted by stars.

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

Spec Driven Development

MCP Server that facilitates spec-driven development workflows, not just Vibe Coding.

by formulahendryEarly↓ 66/wk★ 440Updated 14 months ago

Runs on your computer

Install

Remote Desktop Commander

Remote Desktop Commander: use files, terminal and processes on your own computers from any AI app.

by desktop-commanderGrowing★ 211Updated 4 days ago

Runs in the cloud✓ desktopcommander.app

Install

phylokit-mcp

Phylogenetic inference via IQ-TREE 3 — never returns a topology without its support

by musharnaVery new↓ 150/wkUpdated today

Runs on your computer

Install

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.

MCP Slim Guard

MCP Slim Guard gives a host one deliberate way to reach authorized upstream tools. It keeps input schemas intact, validates calls before the upstream is invoked, and can recover an oversized result exactly without repeating that invocation.

Choose a mode

Mode	What the host sees	Best fit
Native	Authorized original tool names and full schemas, plus `read_result`	Hosts that work well with a normal MCP catalog, including Codex
Compact	`find_tool`, `call_tool`, and `read_result`; discovery returns each match's full original schema	A small, predictable host surface
Extreme	The Compact tool surface and schemas; only sufficiently large results receive a shorter recoverable first delivery	Context-sensitive hosts where a smaller first result is valuable

Compact is the default for start. Native is the default installation plan for Codex. Compact is the default for Claude Code; Claude Code supports Compact and Extreme installation plans, not Native.

All modes apply the same allow/deny authorization. Compact and Extreme return at most three discovery matches, each with the original required fields, enums, and nested schema. A call is validated against that original schema before the upstream server is contacted.

find_tool rejects unknown fields and queries longer than 256 Unicode code points locally. It searches only the current authorized catalog and never falls back to an unauthorized entry.

Quick start

0.1.1-alpha.2 is a source candidate and is not published to npm yet. From a reviewed checkout of this candidate:

npm ci

npm run build npm link cd /path/to/project-with-mcp-config mcp-slim-guard init mcp-slim-guard validate

Run the default Compact mode.

mcp-slim-guard start

init writes mcp-slim-guard.yml with version 2. The file contains upstream and security settings only. Select a mode in the host command, not in YAML.

# Inspect a host-specific plan without changing host files.

mcp-slim-guard plan --host codex mcp-slim-guard plan --host claude-code --mode extreme

Verify the configured runtime without changing Host configuration or calling a business Tool.

mcp-slim-guard verify --host codex

Apply a reviewed plan.

mcp-slim-guard install --host codex --mode native

Host entries

For Codex, use Native when you want the normal authorized MCP catalog:

[mcp_servers.slim_guard]

command = "mcp-slim-guard" args = ["start", "--mode", "native"] cwd = "/absolute/path/to/project"

For Claude Code, use Compact by default:

"mcpServers": { "slim-guard": { "command": "mcp-slim-guard", "args": ["start", "--mode", "compact"], "cwd": "/absolute/path/to/project" } } }

See host setup for the full configuration and verification steps.

Configuration

version: 2

tools: allow:

"upstream_*" deny:
"*_delete_*"

ssrf: mode: block block_private_ips: true allow_domains: [] block_domains: [] rate_limit: default: "60/min" injection_detection: enabled: true sensitivity: medium mode: block audit: output: file filePath: mcp-slim-guard-audit.log servers: upstream: command: npx args: ["-y", "@your/mcp-server"]

Version 1 configuration is intentionally unsupported. The removed compressor section is rejected rather than migrated automatically.

Repair an invalid call

If arguments do not match an authorized tool's original schema, Slim Guard returns a normal MCP tool error with structuredContent that identifies the schema failure and confirms that the upstream tool was not invoked. Correct the arguments and retry; submitted argument values are not echoed in that error.

Result recovery

When a response needs recoverable delivery, the first response includes a result_ref. Use read_result with query to locate up to three bounded local fragments, or omit query and follow next_cursor to recover the exact snapshot. Both paths use the same immutable capture and never invoke the upstream tool again. Do not combine query with cursor. Native and Compact use the standard delivery boundary. Extreme uses a smaller boundary only when the initial delivered response is at least half the size of the exact response; otherwise it passes the exact response through unchanged.

Evidence and checks

The repository includes a 24-task mode comparison, result-recovery fixtures, and a 100-tool / 8,000-row stress fixture. Run the current artifacts with:

npm run build

npm run bench:task npm run bench:compression npm run bench:stress npm run bench:compression:verify

Their reports are mode-specific and are generated locally; do not treat older alpha benchmark figures as claims for this product line.

Development

npm run build

npm run typecheck npm run lint npm test npm run verify:package-boundary npm run smoke:package

This project is an alpha. Review authorization patterns and upstream settings before using it with privileged tools.

MCP Slim Guard

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 Otheri

Common questions

Alternatives

Spec Driven Development

Remote Desktop Commander

phylokit-mcp

README from the maker

MCP Slim Guard

Choose a mode

Quick start

Run the default Compact mode.

Verify the configured runtime without changing Host configuration or calling a business Tool.

Apply a reviewed plan.

Host entries

Configuration

Repair an invalid call

Result recovery

Evidence and checks

Development