list_messages

THE RISK

Low Risk

Why list_messages needs a policy

This tool retrieves and queries message data with no side effects. It is a straightforward read operation that fetches existing messages without creating, modifying, or deleting data. The low severity reflects minimal risk from misuse—an agent could retrieve conversation history, but this is a standard query operation.

From the tool's definition Tool name is 'list_messages' and description states 'List Messages' with no mention of modification, deletion, or execution. Returns messages with optional date filtering (max 183 days).

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

POLICY

How to control list_messages

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 list_messages:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_messages": {}
  }
}

list_messages is read-only, so it stays allowed — but 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.

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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 add_attachments_to_message Add attachments to a message. In order to add attachments to a message, you must provide a 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

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about list_messages

What does the list_messages tool do? +

List Messages. By default returns latest 20 messages. The maximum allowed range between dates is 183 days (6 months). It is categorised as a Read tool in the Carbon Voice MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on list_messages? +

Register the Carbon Voice MCP server in PolicyLayer and add a rule for list_messages: 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 list_messages? +

list_messages is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_messages? +

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

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

list_messages 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.

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