arc_close_tabs · Arc Browser MCP: Risk & Policy

WHAT IT DOES

What arc_close_tabs does on Arc Browser MCP

AI agents use arc_close_tabs 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_close_tabs needs a policy

An AI agent can call arc_close_tabs faster than any human can review — one bad instruction and it creates or modifies resources in Arc Browser MCP by the hundred, each call as confident as the last.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

arc_close_tabs Rate-limited

arc_close_tabs 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_close_tabs": {
      "limits": [
        {
          "counter": "arc_close_tabs_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_close_tabs

What does the arc_close_tabs tool do? +

Close one or more Arc tabs by explicit tab id. Use dry_run to preview. 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_close_tabs? +

Register the Arc Browser MCP server in PolicyLayer and add a rule for arc_close_tabs: 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_close_tabs? +

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

Can I rate-limit arc_close_tabs? +

Yes. Add a rate_limit block to the arc_close_tabs 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_close_tabs completely? +

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

arc_close_tabs 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.