send_multipart · Bluebubbles MCP: Risk & Policy

WHAT IT DOES

What send_multipart does on Bluebubbles

AI agents use send_multipart 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_multipart needs a policy

The tool sends messages (likely multipart/multimedia messages based on the name), which modifies data on the BlueBubbles server and recipient's devices. This is reversible via the 'delete_message' or 'edit_message' sibling tools, placing it in Write rather than Destructive.

From the tool's definition Tool name 'send_multipart' combined with server description stating it 'allow[s] users to...send messages directly from MCP clients.' Sibling tools include send-related operations and the server manages iMessage communications.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send_multipart Rate-limited

send_multipart 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_multipart": {
      "limits": [
        {
          "counter": "send_multipart_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_multipart

What does the send_multipart tool do? +

send_multipart. 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_multipart? +

Register the Bluebubbles MCP server in PolicyLayer and add a rule for send_multipart: 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_multipart? +

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

Can I rate-limit send_multipart? +

Yes. Add a rate_limit block to the send_multipart 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_multipart completely? +

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

send_multipart 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.