add_label_to_message

THE RISK

Medium Risk

Why add_label_to_message needs a policy

This is a Write operation because it creates or modifies data reversibly. Adding a label to a message changes the message's metadata and organizational state but does not delete data or trigger external actions. The operation can be undone by removing the label.

From the tool's definition The tool 'add_label_to_message' modifies message metadata by adding a label. The server description states it enables 'read, compose, and send emails', and this sibling tool performs a reversible modification operation on existing messages.

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

POLICY

How to control add_label_to_message

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "add_label_to_message": {
      "limits": [
        {
          "counter": "add_label_to_message_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

add_label_to_message stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

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

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Mcp Gmail tools

Write remove_label_from_message Remove a label from a message. Write compose_email compose_email Write mark_message_read Mark a message as read by removing the UNREAD label. Write send_email Compose and send an email. Read get_emails Get the content of multiple email messages by their IDs. Read list_available_labels Get all available Gmail labels for the user. Read query_emails Search for emails using a raw Gmail query string. Read search_emails search_emails

All 9 Mcp Gmail tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about add_label_to_message

What does the add_label_to_message tool do? +

Add a label to a message. It is categorised as a Write tool in the Mcp Gmail MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_label_to_message? +

Register the Mcp Gmail MCP server in PolicyLayer and add a rule for add_label_to_message: 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 Gmail. Nothing to install.

What risk level is add_label_to_message? +

add_label_to_message is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit add_label_to_message? +

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

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

add_label_to_message is provided by the Mcp Gmail MCP server (jeremyjordan/mcp-gmail). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Mcp Gmail tool call.

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

CHECK YOUR STACK →