end_session

THE RISK

Critical Risk

Why end_session needs a policy

Ending and cleaning up a browser session is an irreversible action; once closed, the session state, cookies, and in-progress work are lost and cannot be recovered. This maps to Destructive rather than Execute because it permanently terminates a resource rather than running a task. Severity is medium since it affects only a single session and not broader data, but misuse could disrupt ongoing automation workflows.

From the tool's definition 'Closes the specified browser session and cleans up resources' — terminates and cleans up a session irreversibly

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

POLICY

How to control end_session

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

policy.json

{
  "version": "1",
  "default": "deny",
  "hide": [
    "end_session"
  ]
}

end_session disappears from the agent's tool list entirely, and any attempt to call it is denied. The rest of the server keeps working.

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

RESTRICT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Nova Act tools

Execute execute_instruction Executes a natural language instruction in an active browser session. Use task for the mai Execute start_session Starts and initializes a new browser session controlled by Nova Act, navigating to the spe Execute compress_logs Compresses Nova Act log files to reduce size while preserving important information. Optio Read fetch_file Retrieves the contents of a file from the server, with optional base64 encoding. Primarily Read inspect_browser Retrieves current state (URL, title) of an active browser session. Screenshot is omitted b Read list_browser_sessions Lists all active Nova Act browser sessions managed by this MCP server. Returns details abo Read view_compressed_log Retrieves and displays the contents of a compressed log file (.gz) previously created by t Read view_html_log Retrieves and displays HTML log files generated by Nova Act browser sessions. These logs c

All 9 Nova Act tools →

Destructive tools on other servers

Android Forensics ADB MCP Server create_full_backup 0xarchive web3_revoke_key Frida Game Hacking MCP clear_scan cPanel MCP Server clear_spam_box

Go deeper

Critical-risk tools in Nova Act → Every critical-risk tool this server exposes, in one view.
All critical-risk MCP tools → Every critical-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Blast radius → How much damage one compromised or confused agent can do — and how to bound it.
Tool call approval → Approval gates on individual tool calls: auto-allow, prompt, or deny.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about end_session

What does the end_session tool do? +

Closes the specified browser session and cleans up resources. Call this when done with a session. It is categorised as a Destructive tool in the Nova Act MCP Server, which means it can permanently delete or destroy data. Block by default and require explicit approval.

How do I enforce a policy on end_session? +

Register the Nova Act MCP server in PolicyLayer and add a rule for end_session: 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 Nova Act. Nothing to install.

What risk level is end_session? +

end_session is a Destructive tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.

Can I rate-limit end_session? +

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

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

end_session is provided by the Nova Act MCP server (madtank/nova-act-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Nova Act tool call.

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

CHECK YOUR STACK →