file_edit

THE RISK

Medium Risk

Why file_edit needs a policy

file_edit modifies file contents reversibly through text replacement, making it a Write operation rather than Destructive (no deletion or data loss). However, severity is high because: (1) it operates on workspace files which may contain critical configuration or source code, (2) malicious text replacement could corrupt application logic or configs, (3) the tool is part of a Docker container execution environment…

From the tool's definition Tool description states 'Replace text in a file' - this is a modification operation. The mechanism uses 'exact string matching' to perform targeted edits on file contents.

Documented attack patterns abuse exactly the kind of access file_edit gives an agent:

POLICY

How to control file_edit

PolicyLayer is an MCP gateway — it sits between your AI agents and Docker MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for file_edit:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "file_edit": {
      "limits": [
        {
          "counter": "file_edit_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

file_edit 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.

Create a free account and register Docker MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Docker MCP Server tools

Execute execute_command Execute a shell command. Working directory: ${WORKSPACE} Execute send_input Send input to a running background process Write file_write Create or overwrite a file. Use paths relative to ${WORKSPACE}. Read the file first before Read check_process Check the status of a background process by its ID Read file_glob Find files by glob pattern (e.g., Read file_grep Search for regex patterns in files within ${WORKSPACE}. Read file_ls List files and directories. Use paths relative to ${WORKSPACE}. Read file_read Read a file

All 9 Docker MCP Server tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about file_edit

What does the file_edit tool do? +

Replace text in a file using exact string matching. Use paths relative to ${WORKSPACE}. Read the file first to get exact text to match. It is categorised as a Write tool in the Docker 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 file_edit? +

Register the Docker MCP Server MCP server in PolicyLayer and add a rule for file_edit: 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 Docker MCP Server. Nothing to install.

What risk level is file_edit? +

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

Can I rate-limit file_edit? +

Yes. Add a rate_limit block to the file_edit 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_edit completely? +

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

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

Enforce policy on every Docker MCP Server tool call.

Start from Docker MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →