send_attachment · Bluebubbles MCP: Risk & Policy

WHAT IT DOES

What send_attachment does on Bluebubbles

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

WHY IT NEEDS A POLICY

Why send_attachment needs a policy

This tool sends attachments through iMessage, which modifies the message state and creates new data (sent messages) on the BlueBubbles server and remote endpoints. It is reversible through delete_message, making it Write rather than Destructive. The severity is high because unauthorized use could leak sensitive files to unintended recipients.

From the tool's definition Tool name 'send_attachment' combined with server context showing 'send messages directly' and file transfer capabilities. Sibling tools include message creation and editing operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send_attachment Rate-limited

send_attachment 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": {
    "send_attachment": {
      "limits": [
        {
          "counter": "send_attachment_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 Bluebubbles, so you can run agents against it safely.

FAQ

Questions about send_attachment

What does the send_attachment tool do? +

send_attachment. It is categorised as a Write tool in the Bluebubbles MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on send_attachment? +

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

What risk level is send_attachment? +

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

Can I rate-limit send_attachment? +

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

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

send_attachment is provided by the Bluebubbles MCP server (metaember/bluebubbles-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.