download_attachment
Download a single attachment from a message by its index. Returns base64-encoded content. Warning: large attachments (up to 25 MB) may produce very long responses.
This record as markdown: /tools/trekmail-mcp-server/download-attachment.md
What download_attachment does on TrekMail MCP Server
AI agents call download_attachment to retrieve information from TrekMail MCP Server without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why download_attachment is rated Low
This tool retrieves and returns attachment data from an existing message. It performs a read-only operation with no side effects—no data is created, modified, deleted, or destroyed. The large response size warning does not change the fundamental nature of the operation as a retrieval action. Confidence is high because the description clearly indicates a non-destructive data retrieval operation.
From the tool's definition Tool description states 'Download a single attachment from a message' and 'Returns base64-encoded content', indicating retrieval of existing data without modification or deletion.
Attacks that exploit this kind of access
The rule that runs download_attachment safely
PolicyLayer is an MCP gateway: it sits between your AI agents and TrekMail MCP Server, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For download_attachment, this is the rule to start with:
download_attachment is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect TrekMail MCP Server, apply this rule, and every download_attachment call is checked against it from then on.
Questions about download_attachment
Download a single attachment from a message by its index. Returns base64-encoded content. Warning: large attachments (up to 25 MB) may produce very long responses. It is categorised as a Read tool in the TrekMail MCP Server MCP Server, which means it retrieves data without modifying state.
Register the TrekMail MCP Server MCP server in PolicyLayer and add a rule for download_attachment: 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 TrekMail MCP Server. Nothing to install.
download_attachment 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 download_attachment 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 download_attachment. 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.
download_attachment is provided by the TrekMail MCP Server MCP server (trekmail/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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