rewrite_file

THE RISK

Medium Risk

Why rewrite_file needs a policy

This tool modifies source code by applying heuristic migrations and returning rewritten content. It creates or modifies data (source files) which is reversible in principle but carries high blast radius since automated heuristic rewrites across a codebase can introduce widespread bugs or break functionality if the agent applies incorrect migrations.

From the tool's definition 'Apply heuristic migrations to code and return the rewritten source plus diagnostics' — the tool rewrites file source code

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

POLICY

How to control rewrite_file

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

policy.json

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

rewrite_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.

Create a free account and register HeroUI Migration MCP — 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 HeroUI Migration MCP tools

Write migrate_file_code Applies heuristic transformations to convert HeroUI v2 code to v3 patterns. Read analyze_file Analyze code and return detailed findings about legacy imports, components, props, hooks a Read analyze_legacy_imports Quick heuristic scanner for HeroUI/NextUI v2 imports and symbols. Read analyze_tailwind_config Checks tailwind.config.js for legacy HeroUI plugins and content paths. Read audit_tailwind Analyze a Tailwind configuration file for legacy HeroUI patterns. Read check_v3_compatibility Checks if a file content follows HeroUI v3 patterns (no NextUI, uses compound API). Read compare_component Show presence/status of a component between v2 and v3, with alias lookup. Read corpus_status Checks the presence and metadata of generated documentation artifacts.

All 18 HeroUI Migration MCP 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 rewrite_file

What does the rewrite_file tool do? +

Apply heuristic migrations to code and return the rewritten source plus diagnostics. It is categorised as a Write tool in the HeroUI Migration 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 rewrite_file? +

Register the HeroUI Migration MCP server in PolicyLayer and add a rule for rewrite_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 HeroUI Migration MCP. Nothing to install.

What risk level is rewrite_file? +

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

Can I rate-limit rewrite_file? +

Yes. Add a rate_limit block to the rewrite_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 rewrite_file completely? +

Set action: deny in the PolicyLayer policy for rewrite_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 rewrite_file? +

rewrite_file is provided by the HeroUI Migration MCP server (sctg-development/heroui-migration-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every HeroUI Migration MCP tool call.

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

CHECK YOUR STACK →