Mcp Guard

mcp-guard 🛡️

[](https://golang.org/) [](https://opensource.org/licenses/MIT)

> The local privacy firewall, secret sanitizer, and token compressor for AI coding agents.

A security guardrail proxy for Model Context Protocol (MCP) servers.

mcp-guard is an ultra-fast, zero-dependency Go binary that sits transparently in the stdio JSON-RPC path between your editor (Claude Code, Cursor, VS Code) and any Model Context Protocol (MCP) server.

It acts as a local security proxy—ensuring your sensitive API keys, database credentials, and protected paths (~/.ssh, .env, .git) are never leaked to cloud LLMs or mutated by autonomous tool execution.

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💡 Why mcp-guard?

When AI agents run tools like @modelcontextprotocol/server-filesystem or postgres-mcp, they read raw files directly from your disk. If a file contains AWS keys, JWTs, or database passwords, those credentials are sent directly to cloud AI APIs in plain text.

mcp-guard runs locally on your machine to solve this without breaking agent execution:

• 🔒 Zero-Trust Input/Output Inspection: Intercepts both requests and responses on stdin/stdout.
• ⚡ Zero-Dependency Go Binary: Negligible performance overhead ( Note: Compression automatically skips read-for-edit tools (read_file, get_file_contents) to preserve exact diff boundaries for safe file editing.

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🚀 Installation

# Install via Go
go install github.com/sainitish1609/mcp-guard/cmd/mcp-guard@latest

# Or build from source
git clone https://github.com/sainitish1609/mcp-guard.git
cd mcp-guard
go build -o mcp-guard ./cmd/mcp-guard

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## ⚙️ Configuration & Integration

### Claude Code

Wrap any standard MCP server command using `mcp-guard --`:

```bash
claude mcp add postgres -- mcp-guard --redact-secrets --max-tokens 4000 -- npx -y @modelcontextprotocol/server-postgres

Cursor / VS Code (.vscode/mcp.json)

{
  "mcpServers": {
    "filesystem": {
      "command": "mcp-guard",
      "args": [
        "--redact-secrets",
        "--block-shell",
        "--",
        "npx",
        "-y",
        "@modelcontextprotocol/server-filesystem",
        "/Users/username/projects"
      ]
    }
  }
}

---

📋 Flag Reference

| Flag | Default | Description | | --- | --- | --- | | --redact-secrets | true | Mask API keys, tokens, and database passwords in tool responses | | --block-shell | true | Block execution of shell scripts in exec tools | | --annotate-tools | true | Append policy notices to tools/list so agents know boundaries upfront | | --compress | false | Strip comments and blank lines from context (safe tools only) | | --max-tokens N | 0 | Approximate token budget cap per result block (0 = unlimited) | | --protect-paths | (defaults) | Custom comma-separated protected paths (overrides defaults) | | --log-level | info | Set logging verbosity (silent, error, info, debug on stderr) | | --dry-run | false | Log security events to stderr without mutating stdin/stdout |

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🧪 Testing & Verification

# Run unit and integration tests
go test ./... -v

# Run static analysis
go vet ./...

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📄 License

Distributed under the MIT License. See LICENSE for details.

Source & license

This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: sainitish1609
• Source: sainitish1609/mcp-guard
• License: MIT

Install and usage instructions live in the source repository linked above.