debug_localhost

THE RISK

High Risk

Why debug_localhost needs a policy

This tool executes an external process (browser) and initiates a live debugging session against a localhost target. An AI agent could use this to interact with local services, intercept traffic, or manipulate a running application. The combination of launching a process and attaching a debugger represents significant Execute-level risk with a high blast radius.

From the tool's definition 'Launch browser with a localhost URL and automatically connect for debugging' — launches a browser process and establishes a debugging connection

Documented attack patterns abuse exactly the kind of access debug_localhost gives an agent:

POLICY

How to control debug_localhost

PolicyLayer is an MCP gateway — it sits between your AI agents and Browser Connect, and nothing reaches the server without passing your rules. This is the rule we recommend for debug_localhost:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "debug_localhost": {
      "limits": [
        {
          "counter": "debug_localhost_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

debug_localhost stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register Browser Connect — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Browser Connect tools

Execute browser_launch Launch a new browser instance with debugging enabled Execute performance_profile Advanced performance profiling with bottleneck detection and recommendations Execute backend_debugger_attach Attach to a Node.js process debugger for breakpoint debugging Execute browser_connect Connect to a specific browser tab for debugging Read network_performance Get network performance statistics for a connected browser tab Read backend_logs_stream Stream and search logs from backend applications (files, processes, Docker containers) Read browser_list_tabs List all available browser tabs that can be connected to Read console_advanced_search Advanced console search with pattern matching, correlation, and statistics

All 16 Browser Connect tools →

Execute tools on other servers

Android Forensics ADB MCP Server adb_shell_command EMBA-MCP run_emba_scan Frida Game Hacking MCP remove_breakpoint Procmon request_elevation

Go deeper

High-risk tools in Browser Connect → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about debug_localhost

What does the debug_localhost tool do? +

Launch browser with a localhost URL and automatically connect for debugging. It is categorised as a Execute tool in the Browser Connect MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on debug_localhost? +

Register the Browser Connect MCP server in PolicyLayer and add a rule for debug_localhost: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Browser Connect. Nothing to install.

What risk level is debug_localhost? +

debug_localhost is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit debug_localhost? +

Yes. Add a rate_limit block to the debug_localhost rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block debug_localhost completely? +

Set action: deny in the PolicyLayer policy for debug_localhost. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides debug_localhost? +

debug_localhost is provided by the Browser Connect MCP server (perception30/browser-connect-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Browser Connect tool call.

Start from Browser Connect, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →