browser_upload_file · Awslabs Valkey MCP: Risk & Policy

WHAT IT DOES

What browser_upload_file does on Awslabs Valkey

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

WHY IT NEEDS A POLICY

Why browser_upload_file needs a policy

File upload operations create or add data to a system (Write category). Without a description, confidence is moderate. Severity is medium because uploads can modify system state reversibly and may have moderate blast radius depending on what backend systems process the uploaded file (e.g., in a browser/cache context, uploaded files could impact caching behavior or stored state).

From the tool's definition Tool name 'browser_upload_file' indicates file upload capability. Description is empty, limiting evidential basis.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_upload_file Rate-limited

browser_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": {
    "browser_upload_file": {
      "limits": [
        {
          "counter": "browser_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 Awslabs Valkey, so you can run agents against it safely.

FAQ

Questions about browser_upload_file

What does the browser_upload_file tool do? +

browser_upload_file. It is categorised as a Write tool in the Awslabs Valkey MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on browser_upload_file? +

Register the Awslabs Valkey MCP server in PolicyLayer and add a rule for browser_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 Awslabs Valkey. Nothing to install.

What risk level is browser_upload_file? +

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

Can I rate-limit browser_upload_file? +

Yes. Add a rate_limit block to the browser_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 browser_upload_file completely? +

Set action: deny in the PolicyLayer policy for browser_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 browser_upload_file? +

browser_upload_file is provided by the Awslabs Valkey MCP server (awslabs.valkey-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.