scaffold_hook

THE RISK

Medium Risk

Why scaffold_hook needs a policy

Installing hooks modifies system behavior and configuration files, which qualifies as a Write operation. The severity is medium rather than high because hooks, while affecting system behavior, are typically installable/uninstallable without permanent data loss.

From the tool's definition "Install a Claude Code hook from the toolkit" - the verb "install" indicates creating or modifying system configuration/hooks, which are reversible write operations.

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

POLICY

How to control scaffold_hook

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

policy.json

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

scaffold_hook 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 Toolkit — 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 Toolkit tools

Destructive cleanup_backups Delete old backup files to free up disk space. Destructive wipe_traces Securely wipe ALL Claude Code traces. Overwrites files with zeros before deletion. Require Destructive clean_claude_directory Analyze and clean the .claude directory. Removes debug logs, empty todos, old snapshots, a Destructive clean_traces Selectively clean Claude Code traces by category, age, or project. Destructive enforce_retention Apply data retention policy by deleting sessions older than specified days. Execute run_doctor Full integrity check: detects corrupted JSONL lines, truncated thinking blocks, oversized Execute run_maintenance Run maintenance checks on Claude Code installation. Identifies issues, old backups, and ar Execute start_dashboard Start the web dashboard on a local port. Returns the URL to open in a browser.

All 40 Claude Code Toolkit 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 scaffold_hook

What does the scaffold_hook tool do? +

Install a Claude Code hook from the toolkit. It is categorised as a Write tool in the Claude Code Toolkit MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on scaffold_hook? +

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

What risk level is scaffold_hook? +

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

Can I rate-limit scaffold_hook? +

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

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

scaffold_hook is provided by the Claude Code Toolkit MCP server (asifkibria/claude-code-toolkit). 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 Toolkit tool call.

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

CHECK YOUR STACK →