AI agents call get_size to retrieve information from Imap without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool only queries and retrieves message size information. It has no side effects, does not modify data, does not execute code, and does not delete or move money. It is a simple metadata retrieval operation, consistent with the Read category (get, fetch, retrieval).
From the tool's definition Tool name is 'get_size' and description states 'Read message size for the given uid in directory'—explicitly a read operation that retrieves metadata without modifying or deleting data.
Attacks that exploit this kind of access
Read message size for the given uid in directory. It is categorised as a Read tool in the Imap MCP Server, which means it retrieves data without modifying state.
Register the Imap MCP server in PolicyLayer and add a rule for get_size: 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 Imap. Nothing to install.
get_size 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 get_size 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 get_size. 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.
get_size is provided by the Imap MCP server (vivier/imap-mcp-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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