gmail_list_messages

THE RISK

Low Risk

Why gmail_list_messages needs a policy

This tool retrieves and queries email messages without creating, modifying, or deleting data. It falls squarely within the Read category. The optional search filters do not change the fundamental nature of the operation. Severity is low because the blast radius of misuse is limited to information disclosure of accessible emails, with no destructive or financial impact.

From the tool's definition Tool name contains 'list' and description states 'List messages from Gmail with optional search filters' — a retrieval operation with no modification or deletion capability.

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

POLICY

How to control gmail_list_messages

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

policy.json

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

gmail_list_messages 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 Google Workspace — 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 →

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EXPLORE

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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 gmail_list_messages

What does the gmail_list_messages tool do? +

List messages from Gmail with optional search filters. Args: - query (string, optional): Gmail search query (e.g.,. It is categorised as a Read tool in the Google Workspace MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on gmail_list_messages? +

Register the Google Workspace MCP server in PolicyLayer and add a rule for gmail_list_messages: 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 Google Workspace. Nothing to install.

What risk level is gmail_list_messages? +

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

Can I rate-limit gmail_list_messages? +

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

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

gmail_list_messages is provided by the Google Workspace MCP server (everyinc/google-workspace-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 Google Workspace tool call.

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

CHECK YOUR STACK →