Full message content + headers + attachment list (no bytes).
AI agents call read_email to retrieve information from Nexus Core without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a read operation—it queries and retrieves email data without side effects. It does not create, modify, delete, or execute actions. The emphasis on 'no bytes' for attachments further confirms it is a safe read operation that does not download or process attachment content. Severity is low because reading email has minimal blast radius if misused by an AI agent.
From the tool's definition Tool name is 'read_email' and description states it retrieves 'Full message content + headers + attachment list' with explicit note '(no bytes)', indicating retrieval only with no modification or deletion of data.
Attacks that exploit this kind of access
Full message content + headers + attachment list (no bytes). It is categorised as a Read tool in the Nexus Core MCP Server, which means it retrieves data without modifying state.
Register the Nexus Core MCP server in PolicyLayer and add a rule for read_email: 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 Nexus Core. Nothing to install.
read_email 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 read_email 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 read_email. 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.
read_email is provided by the Nexus Core MCP server (noumenon-ai/nexus-core). 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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