list_folders

THE RISK

Low Risk

Why list_folders needs a policy

This tool queries and returns information about the folder structure of a Yahoo Mail account without creating, modifying, deleting, or executing any operations. It is a straightforward read operation that retrieves metadata about available mailboxes. The severity is low because exposure of folder names and structure poses minimal risk compared to tools that could delete emails or execute arbitrary commands.

From the tool's definition Tool name 'list_folders' and description 'List all available IMAP folders/mailboxes' indicate a retrieval operation with no modification or deletion of data.

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

POLICY

How to control list_folders

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

policy.json

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

list_folders 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 Yahoo Mail — 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

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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 list_folders

What does the list_folders tool do? +

List all available IMAP folders/mailboxes in your Yahoo Mail account. It is categorised as a Read tool in the Yahoo Mail MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_folders? +

Register the Yahoo Mail MCP server in PolicyLayer and add a rule for list_folders: 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 Yahoo Mail. Nothing to install.

What risk level is list_folders? +

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

Can I rate-limit list_folders? +

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

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

list_folders is provided by the Yahoo Mail MCP server (jtokib/yahoo-mail-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 Yahoo Mail tool call.

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

CHECK YOUR STACK →