@dotsetlabs/overwatch

Overwatch

The AI Agent Firewall

Runtime security proxy for MCP (Model Context Protocol). Overwatch protects AI development environments by detecting tool impersonation attacks and enforcing policy-based access control.

The Threat: Tool Shadowing

MCP is the standard protocol for AI agent tool access. While basic RBAC controls who can access tools, it doesn't verify what the tool actually is. This creates a critical attack surface:

• Tool Shadowing (CVE-2025-6514): Malicious MCP servers impersonate legitimate tools (e.g., a fake postgres tool that exfiltrates queries)
• Schema Mutation: Tools change behavior mid-session after initial trust is established
• Name Collisions: Multiple servers expose tools with identical names but different implementations

Traditional firewalls don't monitor MCP traffic. Overwatch is the AI Agent Firewall.

Installation

npm install -g @dotsetlabs/overwatch

Core Features

1. Tool Shadowing Detection (FLAGSHIP)

Cryptographic verification that tools are what they claim to be.

Detection	Severity	Description
Name Collision	Critical	Same tool name from multiple servers with different schemas
Schema Mutation	Critical	Tool definition changed mid-session
Suspicious Description	High	Tool description contains injection patterns
Hash Verification	High	Tool schema hash doesn't match baseline

Tool Shadowing detection is enabled by default with no configuration required.

2. Policy-Based Access Control

Declarative policies for human-in-the-loop control without approval fatigue.

Approval	Effect
[y]	Allow once
[n]	Deny
[5]	Allow for 5 minutes
[s]	Allow for session

3. Audit Logging

Complete audit trail of all MCP tool calls with export support for SIEM integration.

Usage

MCP Security Proxy

# Wrap any MCP server with policy enforcement
overwatch wrap npx @modelcontextprotocol/server-postgres

# Wrap with strict policy
overwatch wrap --policy strict npx @modelcontextprotocol/server-filesystem

Initialize & Diagnose

# Create overwatch.yaml config
overwatch init

# Check configuration
overwatch doctor

Audit Logs

# View recent activity
overwatch logs

# Tail logs in real-time
overwatch logs --tail

# Export for SIEM
overwatch logs --format cef > audit.cef

How Tool Shadowing Detection Works

               ┌─────────────────────────────┐
               │     Tool Shadowing          │
               │     Detector                │
               │ ┌─────────────────────────┐ │
AI Client ───▶│ │ • Hash tool schemas     │ │───▶ MCP Server
               │ │ • Detect collisions     │ │
               │ │ • Monitor mutations     │ │
               │ │ • Flag suspicious desc  │ │
               │ └─────────────────────────┘ │
               └─────────────────────────────┘

Configuration

# overwatch.yaml
servers:
  postgres:
    command: npx @modelcontextprotocol/server-postgres
    policies:
      - tools: ["query", "execute"]
        action: prompt

      - tools: ["*"]
        paths:
          deny: ["/etc/**", "~/.ssh/**"]

defaults:
  action: prompt

audit:
  enabled: true
  path: ~/.overwatch/audit.log
  format: json

Claude Desktop Integration

{
  "mcpServers": {
    "postgres": {
      "command": "overwatch",
      "args": ["wrap", "npx", "@modelcontextprotocol/server-postgres"]
    }
  }
}

CLI Commands

Command	Description
overwatch wrap <cmd>	Wrap an MCP server with security proxy
overwatch start	Start proxy with config file
overwatch init	Create default configuration
overwatch doctor	Diagnose configuration issues
overwatch logs	View audit logs
overwatch stats	View usage statistics
overwatch sessions	Manage active sessions
overwatch policies	View configured policies

Why Overwatch?

What Overwatch Does	What Other Tools Do
Proxies MCP protocol traffic	Unaware of MCP
Detects tool shadowing attacks	No tool verification
Policy at protocol layer	Application-level only
Session-based approvals	All-or-nothing access

Part of Dotset Labs

Overwatch focuses on runtime protection of AI tool operations. For static analysis of AI config files, see Hardpoint.

SCAN (Hardpoint)  →  CONTROL (Overwatch)
Defend against       Stop Tool Shadowing
Rules File Backdoor  and Rogue Agents

License

MIT