bulk_pin

THE RISK

Medium Risk

Why bulk_pin needs a policy

Pinning/unpinning emails modifies email state and organization but does not create, delete, or destroy data—the emails remain intact and the operation is reversible (pins can be toggled on/off). This classifies as Write rather than Read (has side effects) or Destructive (reversible).

From the tool's definition Tool name 'bulk_pin' and description 'Pin or unpin multiple emails' indicates modification of email metadata (pin state) affecting multiple messages. This is a write operation that changes email attributes reversibly.

Risk signalsBulk/mass operation — affects multiple targets

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

POLICY

How to control bulk_pin

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

policy.json

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

bulk_pin 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 Fastmail 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 →

Free to start. No card required.

EXPLORE

Related tools and policies

More Fastmail MCP Server tools

Destructive bulk_delete Delete multiple emails (move to trash) Destructive delete_email Delete an email (move to trash) Write bulk_remove_labels Remove labels from multiple emails simultaneously Write remove_labels Remove specific labels (mailboxes) from an email Write reply_email Reply to an existing email with proper threading headers (In-Reply-To, References). Automa Write test_bulk_operations Test bulk operations by finding recent emails and performing safe operations (mark read/un Write add_labels Add labels (mailboxes) to an email without removing existing ones Write bulk_add_labels Add labels to multiple emails simultaneously

All 38 Fastmail MCP Server tools →

Write tools on other servers

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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 bulk_pin

What does the bulk_pin tool do? +

Pin or unpin multiple emails. It is categorised as a Write tool in the Fastmail 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 bulk_pin? +

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

What risk level is bulk_pin? +

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

Can I rate-limit bulk_pin? +

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

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

bulk_pin is provided by the Fastmail MCP Server MCP server (madllama25/fastmail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Fastmail MCP Server tool call.

Start from Fastmail 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 →