uploadFile · SMART-E2B MCP: Risk & Policy

WHAT IT DOES

What uploadFile does on SMART-E2B

AI agents use uploadFile to create or update resources in SMART-E2B — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your SMART-E2B environment.

WHY IT NEEDS A POLICY

Why uploadFile needs a policy

uploadFile creates new files or modifies existing file state in the sandbox through file upload. This is a Write operation rather than Read (which only retrieves data) or Execute (which runs code). While uploads could theoretically introduce malicious content, the sandboxed nature limits blast radius to the isolated environment, justifying 'medium' severity.

From the tool's definition Tool enables 'Upload a file to the sandbox' - a reversible creation/modification operation that writes data to the sandboxed environment.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

uploadFile Rate-limited

uploadFile 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches SMART-E2B, so you can run agents against it safely.

FAQ

Questions about uploadFile

What does the uploadFile tool do? +

Upload a file to the sandbox. It is categorised as a Write tool in the SMART-E2B MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on uploadFile? +

Register the SMART-E2B MCP server in PolicyLayer and add a rule for uploadFile: 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 SMART-E2B. Nothing to install.

What risk level is uploadFile? +

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

Can I rate-limit uploadFile? +

Yes. Add a rate_limit block to the uploadFile 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 uploadFile completely? +

Set action: deny in the PolicyLayer policy for uploadFile. 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 uploadFile? +

uploadFile is provided by the SMART-E2B MCP server (leghis/smart-e2b). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.