ai_rewrite · Onion MCP: Risk & Policy

WHAT IT DOES

What ai_rewrite does on Onion

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

WHY IT NEEDS A POLICY

Why ai_rewrite needs a policy

This tool rewrites/transforms text content. It creates modified versions of existing text, which is a Write operation. It does not execute code, delete data, or involve finances. The blast radius is low since it only processes text passed to it and returns a rewritten version.

From the tool's definition 改写文本，支持正式化、口语化、简洁化、扩写四种模式 (Rewrite text, supporting four modes: formalization, colloquialization, simplification, and expansion)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

ai_rewrite Rate-limited

ai_rewrite 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": {
    "ai_rewrite": {
      "limits": [
        {
          "counter": "ai_rewrite_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 Onion, so you can run agents against it safely.

FAQ

Questions about ai_rewrite

What does the ai_rewrite tool do? +

改写文本，支持正式化、口语化、简洁化、扩写四种模式。. It is categorised as a Write tool in the Onion MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on ai_rewrite? +

Register the Onion MCP server in PolicyLayer and add a rule for ai_rewrite: 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 Onion. Nothing to install.

What risk level is ai_rewrite? +

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

Can I rate-limit ai_rewrite? +

Yes. Add a rate_limit block to the ai_rewrite 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 ai_rewrite completely? +

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

ai_rewrite is provided by the Onion MCP server (onion-ai/mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.