fix_code

THE RISK

Medium Risk

Why fix_code needs a policy

This tool modifies existing code to fix bugs, which is a write/modification operation. It creates altered versions of code. The severity is medium because while it modifies code it operates on provided code snippets rather than directly writing to the filesystem (based on available description).

From the tool's definition Fixes bugs or issues in the given code

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

POLICY

How to control fix_code

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

policy.json

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

fix_code 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 Claude Code — 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 Claude Code tools

Execute simulate_command Simulates the execution of a given command. Execute your_own_query Sends a custom query with context. Write test_code Generates tests for the given code. Write edit_code Edits the given code based on instructions. Read explain_code Provides detailed explanation of the given code. Read review_code Reviews the given code.

All 7 Claude Code 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 fix_code

What does the fix_code tool do? +

Fixes bugs or issues in the given code. It is categorised as a Write tool in the Claude Code MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on fix_code? +

Register the Claude Code MCP server in PolicyLayer and add a rule for fix_code: 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 Claude Code. Nothing to install.

What risk level is fix_code? +

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

Can I rate-limit fix_code? +

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

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

fix_code is provided by the Claude Code MCP server (kunihiros/claude-code-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Claude Code tool call.

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

CHECK YOUR STACK →