subscribe_user_by_email

THE RISK

Medium Risk

Why subscribe_user_by_email needs a policy

This tool modifies a user's subscription status by adding them to a subscription group. This is a reversible write operation (subscriptions can be changed/removed), not destructive. Misuse could result in users being enrolled in unwanted communications, hence medium severity.

From the tool's definition Subscribe a user to a subscription group by email

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

POLICY

How to control subscribe_user_by_email

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

policy.json

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

subscribe_user_by_email 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 Iterable MCP Server — 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 →

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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 subscribe_user_by_email

What does the subscribe_user_by_email tool do? +

Subscribe a user to a subscription group by email. It is categorised as a Write tool in the Iterable MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on subscribe_user_by_email? +

Register the Iterable MCP Server MCP server in PolicyLayer and add a rule for subscribe_user_by_email: 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 Iterable MCP Server. Nothing to install.

What risk level is subscribe_user_by_email? +

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

Can I rate-limit subscribe_user_by_email? +

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

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

subscribe_user_by_email is provided by the Iterable MCP Server MCP server (iterable/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Iterable MCP Server tool call.

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

CHECK YOUR STACK →