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Secure LLM Access to MCP Servers

MCP Guardian gives real-time logging, approval, and control over your LLM's access to MCP servers.

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Updated Aug 2025
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Source checked Sep 20, 2026
Version 0.6.0
Models
universal
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Why it matters

Manage and secure your LLM's interactions with MCP servers. Gain real-time control over LLM activity, including message logging, confirmations, and automated security checks.

Outcomes

What it gets done

01

Log all LLM activity on MCP servers for auditing.

02

Approve or reject individual LLM tool calls in real-time.

03

Implement automated security and privacy checks for LLM messages.

04

Easily manage multiple MCP server configurations.

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Overview

mcp-guardian MCP Server

MCP Guardian gives real-time logging and an approve/deny gate over an LLM's MCP server tool calls, plus easy multi-server configuration switching. Use it when you want visibility and manual control over what an LLM assistant does through its MCP servers before tool calls execute.

What it does

MCP Guardian manages your LLM assistant's access to MCP servers, giving you real-time control over what it does with them. It sits between the LLM and its MCP servers, logging every message so you can see traces of all MCP server activity, and lets you approve or deny individual tool-call messages as they happen rather than granting blanket access up front.

When to use - and when NOT to

Use it when you want visibility and control over what an LLM assistant is actually doing through its MCP servers - reviewing tool calls before they execute, auditing activity after the fact, or managing several different MCP server configurations without hand-editing config files for each host application every time you switch. Automated message scanning for safety and privacy is explicitly marked as coming soon in the project's own docs, so real-time automated checks beyond manual approval aren't available yet; today's control is manual approve/deny plus logging. It is a governance and proxy layer over MCP servers, not an MCP server that exposes its own tools to an LLM.

Capabilities

Message Logging captures traces for all of an LLM's MCP server activity, giving a complete record to review. Message Approvals let you approve or deny individual tool-call messages in real time as the LLM attempts to use them, putting a human checkpoint in the loop before a call executes. Configuration management lets you switch between different MCP server collections quickly, without manually editing configuration files for each MCP host application every time your setup changes. Automated Message Scans, real-time automated checks for safety and privacy concerns, are planned but not yet shipped.

How to install

There is no packaged install; you build it from source using Nix. On Linux/macOS: install Nix, enable flakes, then:

nix develop
just build-release

The resulting mcp-guardian and mcp-guardian-proxy binaries land in _build/bin/, already on PATH inside the dev shell. On Windows, install Git with symlink support, rustup, Node.js, yarn, the Visual Studio C++ build tools for the required .dll dependencies, and cargo install just, then run the repo from git-bash and just build-release the same way.

Who it's for

Anyone running an LLM assistant against MCP servers who wants a real-time audit trail and an approval gate over its tool calls, plus easy switching between MCP server configurations, instead of trusting the assistant with unmonitored, unmanaged access.

Source README

MCP Guardian

mcp-guardian.org

Overview

MCP Guardian manages your LLM assistant's access to MCP servers, handing you realtime control of your LLM's activity.

📜 Message Logging - See traces for all of an LLM's MCP server activity

💂 Message Approvals - Approve and deny individual tool call messages in real time

🤖 Automated Message Scans - Realtime automated checks for safety, privacy, etc (Coming Soon)

MCP Guardian also makes it a breeze to manage multiple MCP server configurations. Quickly switch between server collections without having to manually manage configuration files for your MCP host applications.

Development

This project uses nix to manage a development environment that can be used on Linux and macOS.

Quick Start - Linux / macOS

  1. Install nix

  2. Enable nix flakes

sudo sh -c 'echo "experimental-features = nix-command flakes" >> /etc/nix/nix.conf'
  1. Enter dev shell
nix develop
  1. Build project
just build-release
  1. mcp-guardian and mcp-guardian-proxy are now in _build/bin/ which is in PATH of the dev shell.

Quick Start - Windows

  1. Install git with symlink support (otherwise you will need to restore ./mcp-guardian/bindings before building).

  2. Install rustup.

  3. Install nodejs.

  4. Install yarn.

npm install --global yarn

  1. Install .dll dependencies. The easiest way to do this is to install Visual Studio and install the C++ development packages.

  2. Install just

cargo install just

  1. Enter repo root with git-bash (otherwise just won't work and you'll need to call cargo directly)

  2. Build project

just build-release

Justfile

Available recipes:
    build
    build-release
    clean
    do DIR +RECIPE
    do-all +RECIPE
    fmt
    fmt-check
    lint
    readme-check
    readme-update
    test

FAQ

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Discussion

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