Download a generated email preview screenshot. Returns base64 content.
AI agents call mailosaur_files_get_preview to retrieve information from Mailosaur MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves a pre-generated preview image (screenshot) of an email. It reads and returns existing data in base64 format without creating, modifying, deleting, or executing any operations. The blast radius of misuse is minimal—an attacker could only access preview screenshots they have permission to view, which are non-sensitive test artifacts in a Mailosaur testing environment.
From the tool's definition Tool description explicitly states 'Download a generated email preview screenshot' and 'Returns base64 content'. The verb 'download' in the context of retrieving a preview file indicates data retrieval without modification or side effects.
Attacks that exploit this kind of access
Download a generated email preview screenshot. Returns base64 content. It is categorised as a Read tool in the Mailosaur MCP MCP Server, which means it retrieves data without modifying state.
Register the Mailosaur MCP server in PolicyLayer and add a rule for mailosaur_files_get_preview: 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 Mailosaur MCP. Nothing to install.
mailosaur_files_get_preview 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 mailosaur_files_get_preview 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 mailosaur_files_get_preview. 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.
mailosaur_files_get_preview is provided by the Mailosaur MCP server (mrnewdelhi/mailosaur-mcp). 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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