List all mailboxes/folders in the FastMail account with names, roles, and counts
AI agents call list_mailboxes to retrieve information from FastMail MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves information about mailbox structure and metadata (names, roles, counts) without creating, modifying, deleting, or executing any operations. It is a read-only query operation with minimal blast radius if misused by an AI agent—only information disclosure about the account's folder structure is at risk.
From the tool's definition Tool name 'list_mailboxes' and description 'List all mailboxes/folders in the FastMail account with names, roles, and counts' indicate a retrieval operation that queries folder metadata without modifying data.
Attacks that exploit this kind of access
List all mailboxes/folders in the FastMail account with names, roles, and counts. It is categorised as a Read tool in the FastMail MCP Server MCP Server, which means it retrieves data without modifying state.
Register the FastMail MCP Server MCP server in PolicyLayer and add a rule for list_mailboxes: 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 FastMail MCP Server. Nothing to install.
list_mailboxes 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_mailboxes 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_mailboxes. 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_mailboxes is provided by the FastMail MCP Server MCP server (jmhron/fastmailmcp). 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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