mail__star_message

THE RISK

Medium Risk

Why mail__star_message needs a policy

Starring or unstarring an email is a reversible metadata modification — it flags/unflags a message without deleting or transmitting any data. This is a Write operation with low blast radius since it only affects a message label/flag.

From the tool's definition Star or unstar an email

Documented attack patterns abuse exactly the kind of access mail__star_message gives an agent:

POLICY

How to control mail__star_message

PolicyLayer is an MCP gateway — it sits between your AI agents and Proton-MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for mail__star_message:

policy.json

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

mail__star_message 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.

Create a free account and register Proton-MCP — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about mail__star_message

What does the mail__star_message tool do? +

Star or unstar an email. It is categorised as a Write tool in the Proton-MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on mail__star_message? +

Register the Proton- MCP server in PolicyLayer and add a rule for mail__star_message: 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 Proton-MCP. Nothing to install.

What risk level is mail__star_message? +

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

Can I rate-limit mail__star_message? +

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

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

mail__star_message is provided by the Proton- MCP server (jorgenclaw/proton-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Proton-MCP tool call.

Start from Proton-MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →