sandbox_fs_list

THE RISK

Low Risk

Why sandbox_fs_list needs a policy

This tool performs a directory listing operation, which is a read-only action that retrieves data about files and directories without creating, modifying, or deleting any content. It has no side effects and presents minimal risk even if misused by an AI agent.

From the tool's definition Tool name 'sandbox_fs_list' and description 'List directory contents inside the sandbox' indicate a query operation that retrieves file system information without modification.

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

POLICY

How to control sandbox_fs_list

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "sandbox_fs_list": {}
  }
}

sandbox_fs_list is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Microsandbox tools

Destructive sandbox_fs_remove Remove a file or directory inside the sandbox. Destructive sandbox_remove Remove a sandbox. Must be stopped unless force is true. Destructive volume_remove Remove a named volume. Execute sandbox_run Create an ephemeral sandbox, run a shell command, return the output, and destroy the sandb Execute sandbox_exec Execute a command inside a running sandbox and return stdout/stderr/exit code. Execute sandbox_shell Execute a shell command or script string inside a running sandbox. Execute sandbox_stop Stop a running sandbox. Use force to kill with SIGKILL instead of graceful SIGTERM. Execute sandbox_create Create and boot a persistent named sandbox with full configuration.

All 19 Microsandbox tools →

Read tools on other servers

M-Team MCP Server get_torrent_detail YouTube MCP Server search_channel Android Forensics ADB MCP Server parse_browser_history 0xarchive web3_challenge

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about sandbox_fs_list

What does the sandbox_fs_list tool do? +

List directory contents inside the sandbox. It is categorised as a Read tool in the Microsandbox MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on sandbox_fs_list? +

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

What risk level is sandbox_fs_list? +

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

Can I rate-limit sandbox_fs_list? +

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

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

sandbox_fs_list is provided by the Microsandbox MCP server (superradcompany/microsandbox-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Microsandbox tool call.

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

CHECK YOUR STACK →