fs_write

A write tool on the Container- MCP server.

SERVERContainer-MCP SOURCE54rt1n/container-mcp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/54rt1n-container-mcp/fs-write.md

WHAT IT DOES

What fs_write does on Container-MCP

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

RISK

Why fs_write is rated Medium

fs_write creates or modifies files in the sandboxed environment. While it cannot permanently damage the host system due to the containerized nature, it can reversibly modify data within the sandbox, making it a Write operation rather than Execute (which would run code) or Destructive (which would irreversibly delete).

From the tool's definition Tool name 'fs_write' and server description indicating it provides sandboxed file system operations. The name explicitly indicates writing/creating file content.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs fs_write safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Container-MCP, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For fs_write, this is the rule to start with:

fs_write Rate-limited

fs_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": {
    "fs_write": {
      "limits": [
        {
          "counter": "fs_write_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Container-MCP, apply this rule, and every fs_write call is checked against it from then on.

FAQ

Questions about fs_write

What does the fs_write tool do? +

fs_write is a write tool on the Container MCP server. It is categorised as a Write tool in the Container-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 fs_write? +

Register the Container MCP server in PolicyLayer and add a rule for fs_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 Container-MCP. Nothing to install.

What risk level is fs_write? +

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

Can I rate-limit fs_write? +

Yes. Add a rate_limit block to the fs_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 fs_write completely? +

Set action: deny in the PolicyLayer policy for fs_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 fs_write? +

fs_write is provided by the Container MCP server (54rt1n/container-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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