relay_create_random_mask · Firefox Relay MCP: Risk & Policy

WHAT IT DOES

What relay_create_random_mask does on Firefox Relay

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

WHY IT NEEDS A POLICY

Why relay_create_random_mask needs a policy

Creating a Firefox Relay mask is a write operation that generates new data. While it modifies the user's email alias configuration, the action is reversible (masks can be disabled via relay_disable_random_mask), so it does not qualify as destructive.

From the tool's definition Tool name contains 'create' and description states 'Create a new Firefox Relay random mask', indicating it creates new data (email masks). This is reversible via the sibling tool 'relay_disable_random_mask'.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

relay_create_random_mask Rate-limited

relay_create_random_mask 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": {
    "relay_create_random_mask": {
      "limits": [
        {
          "counter": "relay_create_random_mask_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 Firefox Relay, so you can run agents against it safely.

FAQ

Questions about relay_create_random_mask

What does the relay_create_random_mask tool do? +

Create a new Firefox Relay random mask. It is categorised as a Write tool in the Firefox Relay MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on relay_create_random_mask? +

Register the Firefox Relay MCP server in PolicyLayer and add a rule for relay_create_random_mask: 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 Firefox Relay. Nothing to install.

What risk level is relay_create_random_mask? +

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

Can I rate-limit relay_create_random_mask? +

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

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

relay_create_random_mask is provided by the Firefox Relay MCP server (nazar256/firefox-relay-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.