watch_start · Musubix MCP: Risk & Policy

WHAT IT DOES

What watch_start does on Musubix

AI agents invoke watch_start to trigger actions in Musubix. 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 watch_start needs a policy

This tool triggers automatic execution of lint, test, and security processes whenever monitored files change. It initiates ongoing background execution of external operations (lint/test/security checks), placing it in the Execute category. Misuse could cause unintended repeated execution of scripts or security scans, but it does not inherently destroy data or move money.

From the tool's definition 'Start file watching and auto-validation. Monitors files for changes and runs lint/test/security automatically'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

watch_start Rate-limited

watch_start 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": {
    "watch_start": {
      "limits": [
        {
          "counter": "watch_start_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 Musubix, so you can run agents against it safely.

FAQ

Questions about watch_start

What does the watch_start tool do? +

Start file watching and auto-validation. Monitors files for changes and runs lint/test/security automatically. It is categorised as a Execute tool in the Musubix MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on watch_start? +

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

What risk level is watch_start? +

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

Can I rate-limit watch_start? +

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

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

watch_start is provided by the Musubix MCP server (@nahisaho/musubix-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.