write_txt · Claude File Management Server MCP: Risk & Policy

WHAT IT DOES

What write_txt does on Claude File Management Server

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

WHY IT NEEDS A POLICY

Why write_txt needs a policy

This tool creates or modifies a text file (New.txt) reversibly. The operations 'write' and 'append' are characteristic of Write category—data can be edited or recovered. Severity is medium because uncontrolled writes could corrupt important data or fill storage, but the effect is reversible. Confidence is high because the description and name clearly denote write-only semantics with no destructive capability.

From the tool's definition Tool name 'write_txt' and description 'Write or append content to New.txt' explicitly indicate content modification operations without deletion or destruction.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

write_txt Rate-limited

write_txt 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_txt": {
      "limits": [
        {
          "counter": "write_txt_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 Claude File Management Server, so you can run agents against it safely.

FAQ

Questions about write_txt

What does the write_txt tool do? +

Write or append content to New.txt. It is categorised as a Write tool in the Claude File Management 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_txt? +

Register the Claude File Management Server MCP server in PolicyLayer and add a rule for write_txt: 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 Claude File Management Server. Nothing to install.

What risk level is write_txt? +

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

Can I rate-limit write_txt? +

Yes. Add a rate_limit block to the write_txt 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_txt completely? +

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

write_txt is provided by the Claude File Management Server MCP server (vipin1000/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.