download_file

THE RISK

Medium Risk

Why download_file needs a policy

This tool fetches content from an external URL and writes it to the local filesystem. It is a Write operation (creating/overwriting a file). The severity is high because a misused agent could download malicious content or overwrite critical files at any specified path, potentially compromising the system.

From the tool's definition Download a file from a URL and save it to a specified path

Documented attack patterns abuse exactly the kind of access download_file gives an agent:

POLICY

How to control download_file

PolicyLayer is an MCP gateway — it sits between your AI agents and MCP Project Standards Server, and nothing reaches the server without passing your rules. This is the rule we recommend for download_file:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "download_file": {
      "limits": [
        {
          "counter": "download_file_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

download_file stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register MCP Project Standards Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

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All 11 MCP Project Standards Server tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about download_file

What does the download_file tool do? +

Download a file from a URL and save it to a specified path. Supported schemes: http, https. It is categorised as a Write tool in the MCP Project Standards Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on download_file? +

Register the MCP Project Standards Server MCP server in PolicyLayer and add a rule for download_file: 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 MCP Project Standards Server. Nothing to install.

What risk level is download_file? +

download_file is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit download_file? +

Yes. Add a rate_limit block to the download_file 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.

How do I block download_file completely? +

Set action: deny in the PolicyLayer policy for download_file. 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.

What MCP server provides download_file? +

download_file is provided by the MCP Project Standards Server MCP server (liliangshan/mcp-server-project-standards). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MCP Project Standards Server tool call.

Start from MCP Project Standards Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →