arc_open_url · Arc Browser MCP: Risk & Policy

WHAT IT DOES

What arc_open_url does on Arc Browser MCP

AI agents use arc_open_url to create or update resources in Arc Browser MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Arc Browser MCP environment.

WHY IT NEEDS A POLICY

Why arc_open_url needs a policy

Opening/navigating a URL modifies the state of a browser tab by changing its location. This is a reversible write action (the tab can be navigated back or to a different URL). It does not execute arbitrary code, delete data, or move money, though it could be misused to navigate to malicious URLs.

From the tool's definition Navigate a specific Arc tab, or the active tab when explicitly omitted.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

arc_open_url Rate-limited

arc_open_url stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "arc_open_url": {
      "limits": [
        {
          "counter": "arc_open_url_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Arc Browser MCP, so you can run agents against it safely.

FAQ

Questions about arc_open_url

What does the arc_open_url tool do? +

Navigate a specific Arc tab, or the active tab when explicitly omitted. It is categorised as a Write tool in the Arc Browser MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on arc_open_url? +

Register the Arc Browser MCP server in PolicyLayer and add a rule for arc_open_url: 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 Arc Browser MCP. Nothing to install.

What risk level is arc_open_url? +

arc_open_url is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit arc_open_url? +

Yes. Add a rate_limit block to the arc_open_url 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 arc_open_url completely? +

Set action: deny in the PolicyLayer policy for arc_open_url. 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 arc_open_url? +

arc_open_url is provided by the Arc Browser MCP server (jasoncronje/arc-browser-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.