clear_session

THE RISK

Critical Risk

Clearing a session's state and history is an irreversible operation — all variables, imports, and execution history within that session are permanently lost. While it doesn't delete files or external data, the in-memory state and history cannot be recovered after clearing, making it Destructive rather than Write.

From the tool's definition Clear a REPL session's state and history

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

HOW TO CONTROL CLEAR_SESSION

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

policy.json

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

clear_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 MCP Python Interpreter — 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

More MCP Python Interpreter tools

Execute run_python_code run_python_code Execute run_python_file Execute a Python file (always uses subprocess for file execution). Args: Execute install_package Install a Python package in the specified environment. Args: package_name Write write_file Write content to a file. Args: file_path: Path to the file to write Read list_directory List all Python files in a directory. Args: directory_path: Path to direc Read list_installed_packages List installed packages for a specific Python environment. Args: environm Read list_python_environments List all available Python environments (system Python and conda environments). Read list_sessions List all active REPL sessions.

All 10 MCP Python Interpreter tools →

Destructive tools on other servers

Frida Game Hacking MCP clear_scan MegaMemory remove_concept Frida Agent MCP kill_app 1MCP Server mcp_uninstall

Go deeper

Critical-risk tools in MCP Python Interpreter → 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.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

What does the clear_session tool do? +

Clear a REPL session's state and history. Args: session_id: Session ID to clear. It is categorised as a Destructive tool in the MCP Python Interpreter 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 clear_session? +

Register the MCP Python Interpreter MCP server in PolicyLayer and add a rule for clear_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 MCP Python Interpreter. Nothing to install.

What risk level is clear_session? +

clear_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 clear_session? +

Yes. Add a rate_limit block to the clear_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 clear_session completely? +

Set action: deny in the PolicyLayer policy for clear_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 clear_session? +

clear_session is provided by the MCP Python Interpreter MCP server (yzfly/mcp-python-interpreter). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MCP Python Interpreter tool call.

Deterministic rules across all 10 MCP Python Interpreter tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.

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10 MCP Python Interpreter tools catalogued and risk-classified — across an index of 42,500+ MCP servers.

// WHAT CLEAR_SESSION ON MCP PYTHON INTERPRETER DOES

// THE RISK

// HOW TO CONTROL CLEAR_SESSION

// EXPLORE