set_active_tab

Set active tab (tab id)

SERVERBrowser SOURCEmcp-server-browser

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/browser/set-active-tab.md

WHAT IT DOES

What set_active_tab does on Browser

AI agents invoke set_active_tab to trigger actions in Browser. 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 set_active_tab is rated High

Switching the active tab is a browser control action with side effects (changes UI state and focus), placing it in the Execute category. While not destructive or data-modifying, it triggers an external operation in the browser. Misuse could redirect agent attention or disrupt user workflow, but blast radius is relatively limited.

From the tool's definition Set active tab (tab id) — triggers a browser action that changes the active/focused tab

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs set_active_tab safely

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

set_active_tab Rate-limited

set_active_tab 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": {
    "set_active_tab": {
      "limits": [
        {
          "counter": "set_active_tab_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 Browser, apply this rule, and every set_active_tab call is checked against it from then on.

FAQ

Questions about set_active_tab

What does the set_active_tab tool do? +

Set active tab (tab id). It is categorised as a Execute tool in the Browser MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on set_active_tab? +

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

What risk level is set_active_tab? +

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

Can I rate-limit set_active_tab? +

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

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

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

KEEP EXPLORING

More on Browser, and thousands of servers like it.

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All 19 Browser tools → High-risk tools on this server →

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Guides

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