set_labels · Mail MCP: Risk & Policy

WHAT IT DOES

What set_labels does on Mail

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

WHY IT NEEDS A POLICY

Why set_labels needs a policy

Setting labels modifies email message state reversibly—labels can be added, removed, or changed without deleting data or executing code. This is a write operation with medium blast radius: an agent could mislabel large quantities of messages (potential disruption to email organization and filtering) but cannot permanently delete data, move money, or execute arbitrary code.

From the tool's definition Tool name 'set_labels' on an IMAP/SMTP email server indicates modification of message metadata (labels/tags). IMAP supports label operations which are reversible write operations on email messages.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_labels Rate-limited

set_labels 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": {
    "set_labels": {
      "limits": [
        {
          "counter": "set_labels_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 Mail, so you can run agents against it safely.

FAQ

Questions about set_labels

What does the set_labels tool do? +

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

How do I enforce a policy on set_labels? +

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

What risk level is set_labels? +

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

Can I rate-limit set_labels? +

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

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

set_labels is provided by the Mail MCP server (kpihx/mail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.