flow_upload_file · DevFlow MCP Server MCP: Risk & Policy

WHAT IT DOES

What flow_upload_file does on DevFlow MCP Server

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

WHY IT NEEDS A POLICY

Why flow_upload_file needs a policy

This tool creates or attaches new files to a flow state, which modifies the flow's data structure. It is reversible (files can typically be removed), so it falls under Write rather than Destructive. The medium severity reflects that unauthorized file uploads could introduce malicious content into development workflows, but the impact is contained to the flow context and the attachment mechanism itself.

From the tool's definition Tool name 'flow_upload_file' and description 'Attach a file from disk to the current flow' indicates file creation/attachment operations. The 50 MB size limit confirms it handles actual file uploads.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

flow_upload_file Rate-limited

flow_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": {
    "flow_upload_file": {
      "limits": [
        {
          "counter": "flow_upload_file_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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

FAQ

Questions about flow_upload_file

What does the flow_upload_file tool do? +

Attach a file from disk to the current flow. Use this for images / PDFs / large files (up to 50 MB).\n\n. It is categorised as a Write tool in the DevFlow 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 flow_upload_file? +

Register the DevFlow MCP Server MCP server in PolicyLayer and add a rule for flow_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 DevFlow MCP Server. Nothing to install.

What risk level is flow_upload_file? +

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

Can I rate-limit flow_upload_file? +

Yes. Add a rate_limit block to the flow_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 flow_upload_file completely? +

Set action: deny in the PolicyLayer policy for flow_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 flow_upload_file? +

flow_upload_file is provided by the DevFlow MCP Server MCP server (klausfreiberufler/devflow-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.