write_file · Friday MCP Server MCP: Risk & Policy

WHAT IT DOES

What write_file does on Friday MCP Server

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

WHY IT NEEDS A POLICY

Why write_file needs a policy

This tool creates or modifies files, which is a reversible Write operation. It has medium severity because uncontrolled file writes in a workspace could corrupt configuration files, overwrite important data, or introduce malicious content, but the effects are theoretically recoverable and scoped to the workspace. Confidence is high given the explicit and unambiguous description.

From the tool's definition Tool name is 'write_file' and description states it will 'Write a file within the workspace.' This directly indicates file creation or modification operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

write_file Rate-limited

write_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": {
    "write_file": {
      "limits": [
        {
          "counter": "write_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 Friday MCP Server, so you can run agents against it safely.

FAQ

Questions about write_file

What does the write_file tool do? +

Write a file within the workspace. It is categorised as a Write tool in the Friday 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 write_file? +

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

What risk level is write_file? +

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

Can I rate-limit write_file? +

Yes. Add a rate_limit block to the write_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 write_file completely? +

Set action: deny in the PolicyLayer policy for write_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 write_file? +

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