browser_close

THE RISK

Low Risk

Why browser_close needs a policy

The description is empty, making it difficult to classify with confidence. Based solely on the name 'browser_close', this appears to terminate a browser session, which is a localized action with minimal blast radius. It doesn't clearly fit Read, Write, Execute, Destructive, or Financial categories as closing a browser is a cleanup/termination action. Confidence is low due to missing description.

From the tool's definition Tool name is 'browser_close' but description is empty and uninformative. The tool name suggests closing a browser instance.

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

POLICY

How to control browser_close

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "browser_close": {
      "limits": [
        {
          "counter": "browser_close_rate",
          "window": "minute",
          "max": 60,
          "scope": "grant"
        }
      ]
    }
  }
}

browser_close gets a rate cap, and everything else on the server is denied unless you say otherwise.

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

SET A RULE FOR THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Tool risk categories → How PolicyLayer classifies MCP tools by what they can do.
MCP tool → What an MCP tool is and how clients discover and call it.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about browser_close

What does the browser_close tool do? +

browser_close. It is categorised as a Other tool in the Prometheus MCP Server MCP Server, which means it performs auxiliary operations.

How do I enforce a policy on browser_close? +

Register the Prometheus MCP Server MCP server in PolicyLayer and add a rule for browser_close: 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 Prometheus MCP Server. Nothing to install.

What risk level is browser_close? +

browser_close is a Other tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit browser_close? +

Yes. Add a rate_limit block to the browser_close 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_close completely? +

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

browser_close is provided by the Prometheus MCP Server MCP server (awslabs.prometheus-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Prometheus MCP Server tool call.

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

CHECK YOUR STACK →