upload-file · OpenAI Assistant MCP Server MCP: Risk & Policy

WHAT IT DOES

What upload-file does on OpenAI Assistant MCP Server

AI agents use upload-file to create or update resources in OpenAI Assistant MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your OpenAI Assistant MCP Server environment.

WHY IT NEEDS A POLICY

Why upload-file needs a policy

This tool creates or stores data (a file upload) in OpenAI's infrastructure, which is a Write operation. It is not Destructive because the file can be deleted. It is not Execute because it does not run code or trigger external operations based on file content.

From the tool's definition Tool name 'upload-file' and description 'Upload a file for use by assistants' indicates creation of new file data in OpenAI's system. The operation is reversible via the sibling tool 'delete-file'.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

upload-file Rate-limited

upload-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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "upload-file": {
      "limits": [
        {
          "counter": "upload-file_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 OpenAI Assistant MCP Server, so you can run agents against it safely.

FAQ

Questions about upload-file

What does the upload-file tool do? +

Upload a file for use by assistants. It is categorised as a Write tool in the OpenAI Assistant MCP 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 upload-file? +

Register the OpenAI Assistant MCP Server MCP server in PolicyLayer and add a rule for upload-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 OpenAI Assistant MCP Server. Nothing to install.

What risk level is upload-file? +

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

Can I rate-limit upload-file? +

Yes. Add a rate_limit block to the upload-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 upload-file completely? +

Set action: deny in the PolicyLayer policy for upload-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 upload-file? +

upload-file is provided by the OpenAI Assistant MCP Server MCP server (snilld-ai/openai-assistant-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.