create_filter · Gmail MCP: Risk & Policy

WHAT IT DOES

What create_filter does on Gmail

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

WHY IT NEEDS A POLICY

Why create_filter needs a policy

Creating a filter is a reversible modification to account configuration. It does not execute code or delete data, but it does create a new persistent rule that will affect email processing (e.g., auto-labeling, archiving, or deleting future emails matching criteria). This is a Write-category action because it modifies account state.

From the tool's definition Tool description states 'Creates a new Gmail filter' — a Gmail filter is a persistent rule that modifies how emails are processed going forward.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_filter Rate-limited

create_filter 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": {
    "create_filter": {
      "limits": [
        {
          "counter": "create_filter_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 Gmail, so you can run agents against it safely.

FAQ

Questions about create_filter

What does the create_filter tool do? +

Creates a new Gmail filter with custom criteria and actions. It is categorised as a Write tool in the 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 create_filter? +

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

What risk level is create_filter? +

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

Can I rate-limit create_filter? +

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

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

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