browser_tab_new

Open a new tab

SERVERCowork Bench SOURCE0717376/cowork_bench

High RISK CLASS

Category Execute

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/cowork-bench/browser-tab-new.md

WHAT IT DOES

What browser_tab_new does on Cowork Bench

AI agents invoke browser_tab_new to trigger actions in Cowork Bench. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.

RISK

Why browser_tab_new is rated High

Browser tab operations fall under Execute because they trigger external actions on a browser system, even though the immediate effect (opening a tab) is relatively benign. The severity is medium because while the tool itself doesn't directly access sensitive data or perform destructive operations, it enables arbitrary navigation and potential exploitation of browser context (cookies, credentials, scripts).

From the tool's definition The tool description states 'Open a new tab', which triggers an external browser operation. Opening a new tab is a browser action that executes an external operation whose effects depend on subsequent navigation/usage.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs browser_tab_new safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Cowork Bench, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For browser_tab_new, this is the rule to start with:

browser_tab_new Rate-limited

browser_tab_new 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.

View as policy code

policy.json

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

RATE-LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Cowork Bench, apply this rule, and every browser_tab_new call is checked against it from then on.

FAQ

Questions about browser_tab_new

What does the browser_tab_new tool do? +

Open a new tab. It is categorised as a Execute tool in the Cowork Bench MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on browser_tab_new? +

Register the Cowork Bench MCP server in PolicyLayer and add a rule for browser_tab_new: 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 Cowork Bench. Nothing to install.

What risk level is browser_tab_new? +

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

Can I rate-limit browser_tab_new? +

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

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

browser_tab_new is provided by the Cowork Bench MCP server (0717376/cowork_bench). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

KEEP EXPLORING

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