add_attachments_to_message

THE RISK

Medium Risk

Why add_attachments_to_message needs a policy

The tool modifies message data by adding attachments, making it a Write operation rather than Read (which would only retrieve data). It is not Destructive because attachments can typically be removed. It is not Execute because it doesn't run code or trigger external operations based on dynamic arguments—it simply attaches files to a message.

From the tool's definition Tool description states "Add attachments to a message" which modifies an existing message by appending attachments to it. This is a reversible modification operation.

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

POLICY

How to control add_attachments_to_message

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

policy.json

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

add_attachments_to_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 Carbon Voice — 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

Related tools and policies

More Carbon Voice tools

Destructive delete_folder Delete a folder by its ID. Deleting a folder will also delete nested folders and all the m Execute run_ai_action Run an AI Action (Prompt) for a message. You can run an AI Action for a message by its ID Execute run_ai_action_for_shared_link Run an AI Action (Prompt) for a shared link. You can run an AI Action for a shared link by Write create_conversation_message Sends a message to an existing conversation or any type with a conversation_id. Write create_direct_message Send a Direct Message (DM) to a User or a Group of Users. Write create_folder Create a new folder. Write create_voicememo_message Create a VoiceMemo Message. In order to create a VoiceMemo Message, you must provide a tra Write move_folder Move a folder by its ID. Move a Folder into another Folder or into a Workspace.

All 28 Carbon Voice tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

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 add_attachments_to_message

What does the add_attachments_to_message tool do? +

Add attachments to a message. In order to add attachments to a message, you must provide a message id and the attachments. It is categorised as a Write tool in the Carbon Voice MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_attachments_to_message? +

Register the Carbon Voice MCP server in PolicyLayer and add a rule for add_attachments_to_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 Carbon Voice. Nothing to install.

What risk level is add_attachments_to_message? +

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

Can I rate-limit add_attachments_to_message? +

Yes. Add a rate_limit block to the add_attachments_to_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 add_attachments_to_message completely? +

Set action: deny in the PolicyLayer policy for add_attachments_to_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 add_attachments_to_message? +

add_attachments_to_message is provided by the Carbon Voice MCP server (phononx/cv-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 Carbon Voice tool call.

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

CHECK YOUR STACK →