AI agents call closeBrowser to permanently remove resources in PlayMCP Browser Automation Server — typically in cleanup and lifecycle workflows. It does its job in a single call, and there is no undo.
Closing the browser is an irreversible action that destroys the current browser session, including all tabs, navigation history, and in-memory state. It cannot be undone without restarting a new session, making it Destructive. Severity is medium because it affects the automation session state but not external data.
From the tool's definition 'Close the browser' — terminates the browser session irreversibly, destroying all open tabs, session state, cookies, and unsaved context.
Documented attack patterns abuse exactly the kind of access closeBrowser gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and PlayMCP Browser Automation Server, and nothing reaches the server without passing your rules. This is the rule we recommend for closeBrowser:
{
"version": "1",
"default": "deny",
"hide": [
"closeBrowser"
]
}closeBrowser disappears from the agent's tool list entirely, and any attempt to call it is denied. The rest of the server keeps working.
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Close the browser. It is categorised as a Destructive tool in the PlayMCP Browser Automation Server MCP Server, which means it can permanently delete or destroy data. Block by default and require explicit approval.
Register the PlayMCP Browser Automation Server MCP server in PolicyLayer and add a rule for closeBrowser: 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 PlayMCP Browser Automation Server. Nothing to install.
closeBrowser is a Destructive tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.
Yes. Add a rate_limit block to the closeBrowser 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.
Set action: deny in the PolicyLayer policy for closeBrowser. 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.
closeBrowser is provided by the PlayMCP Browser Automation Server MCP server (jomon003/playmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from PlayMCP Browser Automation Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
38 PlayMCP Browser Automation Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.