file_write · Universal Dev MCP: Risk & Policy

WHAT IT DOES

What file_write does on Universal Dev MCP

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

WHY IT NEEDS A POLICY

Why file_write needs a policy

The tool creates or modifies files, which is reversible (files can be edited or deleted afterward). This is clearly a Write operation rather than Destructive since files are not permanently removed. The high severity reflects that unrestricted file write access in a development environment could modify source code, configuration files, or dependencies, potentially compromising the integrity of projects.

From the tool's definition Tool name is 'file_write' and description states 'Koi bhi file likhna ya banana' (Hindi: 'write or create any file'). This directly indicates file creation and modification capabilities.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

file_write Rate-limited

file_write 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": {
    "file_write": {
      "limits": [
        {
          "counter": "file_write_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 Universal Dev MCP, so you can run agents against it safely.

FAQ

Questions about file_write

What does the file_write tool do? +

Koi bhi file likhna ya banana. It is categorised as a Write tool in the Universal Dev MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on file_write? +

Register the Universal Dev MCP server in PolicyLayer and add a rule for file_write: 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 Universal Dev MCP. Nothing to install.

What risk level is file_write? +

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

Can I rate-limit file_write? +

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

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

file_write is provided by the Universal Dev MCP server (kallusuvaidyam/universal_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.