swarm_write_file · Mcp Swarm MCP: Risk & Policy

WHAT IT DOES

What swarm_write_file does on Mcp Swarm

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

WHY IT NEEDS A POLICY

Why swarm_write_file needs a policy

The tool creates or modifies files, which is a Write operation. It does not delete data permanently (backups are made), so it does not qualify as Destructive. Severity is high because uncontrolled file writes could corrupt critical application files, configuration, or data if an AI agent misuses it with incorrect paths or content.

From the tool's definition Tool description states '创建或覆盖文件' (create or overwrite file) and '会先备份现有文件' (will first backup existing file). This is a reversible write operation that modifies the filesystem.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

swarm_write_file Rate-limited

swarm_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": {
    "swarm_write_file": {
      "limits": [
        {
          "counter": "swarm_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 Mcp Swarm, so you can run agents against it safely.

FAQ

Questions about swarm_write_file

What does the swarm_write_file tool do? +

创建或覆盖文件。会先备份现有文件。. It is categorised as a Write tool in the Mcp Swarm MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on swarm_write_file? +

Register the Mcp Swarm MCP server in PolicyLayer and add a rule for swarm_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 Mcp Swarm. Nothing to install.

What risk level is swarm_write_file? +

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

Can I rate-limit swarm_write_file? +

Yes. Add a rate_limit block to the swarm_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 swarm_write_file completely? +

Set action: deny in the PolicyLayer policy for swarm_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 swarm_write_file? +

swarm_write_file is provided by the Mcp Swarm MCP server (moselu/mcp-swarm). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.