preview_user_scaffold · Todos MCP: Risk & Policy

WHAT IT DOES

What preview_user_scaffold does on Todos

AI agents invoke preview_user_scaffold to trigger actions in Todos. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why preview_user_scaffold needs a policy

This tool runs code or a template system with user-provided input (variables), which qualifies as Execute. A dry-run typically doesn't persist changes, reducing severity from high to medium, but it can still generate output or side effects depending on what the scaffold contains. The confidence is moderate because the description lacks detail on what scaffolds can do or what side effects might occur during preview.

From the tool's definition Dry-run preview of a user scaffold with variables - executes a scaffold template with provided variables to show the output without persisting changes.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

preview_user_scaffold Rate-limited

preview_user_scaffold stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "preview_user_scaffold": {
      "limits": [
        {
          "counter": "preview_user_scaffold_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Todos, so you can run agents against it safely.

FAQ

Questions about preview_user_scaffold

What does the preview_user_scaffold tool do? +

Dry-run preview of a user scaffold with variables. It is categorised as a Execute tool in the Todos MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on preview_user_scaffold? +

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

What risk level is preview_user_scaffold? +

preview_user_scaffold is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit preview_user_scaffold? +

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

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

preview_user_scaffold is provided by the Todos MCP server (@hasna/todos). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.