gmail_reply · Personal Gmail MCP: Risk & Policy

WHAT IT DOES

What gmail_reply does on Personal Gmail

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

WHY IT NEEDS A POLICY

Why gmail_reply needs a policy

This tool creates and sends new email messages, which is a reversible write operation (emails can be deleted or unsent depending on Gmail's undo window). While email sent is difficult to truly retract, the operation is fundamentally a create/send action rather than destructive deletion.

From the tool's definition Tool description states 'Reply to a message by id' and 'Sends immediately', indicating it creates and sends email content. The replyAll parameter allows modification of recipients, extending the write action's scope.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

gmail_reply Rate-limited

gmail_reply 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_reply": {
      "limits": [
        {
          "counter": "gmail_reply_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about gmail_reply

What does the gmail_reply tool do? +

Reply to a message by id, keeping it in the same thread. Sends immediately. replyAll=true to include all original recipients. It is categorised as a Write tool in the Personal 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 gmail_reply? +

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

What risk level is gmail_reply? +

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

Can I rate-limit gmail_reply? +

Yes. Add a rate_limit block to the gmail_reply 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_reply completely? +

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

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