gmail_message_modify · Google Workspace MCP: Risk & Policy

WHAT IT DOES

What gmail_message_modify does on Google Workspace

AI agents use gmail_message_modify to create or update resources in Google Workspace — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Google Workspace environment.

WHY IT NEEDS A POLICY

Why gmail_message_modify needs a policy

The tool modifies message metadata (labels, read/unread status) but does not delete the message itself or prevent it from being recovered. It is reversible—labels can be re-added and read status can be changed back. This qualifies as Write rather than Destructive.

From the tool's definition Tool description states it can 'Add/remove labels on a message' and gives the example of 'mark read by removing UNREAD'. This is a state modification operation on existing data (labels and read status).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

gmail_message_modify Rate-limited

gmail_message_modify 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.

View as policy code

policy.json

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

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Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Google Workspace, so you can run agents against it safely.

FAQ

Questions about gmail_message_modify

What does the gmail_message_modify tool do? +

Add/remove labels on a message (e.g. mark read by removing UNREAD). It is categorised as a Write tool in the Google Workspace MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on gmail_message_modify? +

Register the Google Workspace MCP server in PolicyLayer and add a rule for gmail_message_modify: 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_message_modify? +

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

Can I rate-limit gmail_message_modify? +

Yes. Add a rate_limit block to the gmail_message_modify 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_message_modify completely? +

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

gmail_message_modify is provided by the Google Workspace MCP server (rajool/google-workspace-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.