AI agents call list_messages to retrieve information from Mcp Imap without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and displays email metadata (subject, sender, date) without modifying, deleting, or executing any actions on the messages. It has no side effects and poses minimal risk of misuse by an AI agent, as viewing message metadata in a folder is a fundamental read operation. Severity is low because the blast radius is limited to information disclosure of already-accessible email headers.
From the tool's definition Tool description states 'List recent messages in a folder with subject, from, date' — a retrieval operation with no modification or deletion.
Attacks that exploit this kind of access
List recent messages in a folder with subject, from, date. Default folder is INBOX. It is categorised as a Read tool in the Mcp Imap MCP Server, which means it retrieves data without modifying state.
Register the Mcp Imap 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 Mcp Imap. Nothing to install.
list_messages is a Read tool with low risk. Read-only tools are generally safe to allow by default.
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.
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.
list_messages is provided by the Mcp Imap MCP server (ngcdan/mcp-imap-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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