play_pattern · Claude DJ MCP: Risk & Policy

WHAT IT DOES

What play_pattern does on Claude DJ MCP

AI agents invoke play_pattern to trigger actions in Claude DJ MCP. 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 play_pattern needs a policy

This tool executes arbitrary code in a browser REPL environment. The effects depend entirely on the pattern code provided as an argument, making it an Execute-category tool. Misuse could involve injecting malicious code into the browser context, hence medium severity.

From the tool's definition 'Send Strudel pattern code to the browser REPL for evaluation. The code will be set and evaluated in the Strudel editor.'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

play_pattern Rate-limited

play_pattern 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": {
    "play_pattern": {
      "limits": [
        {
          "counter": "play_pattern_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 Claude DJ MCP, so you can run agents against it safely.

FAQ

Questions about play_pattern

What does the play_pattern tool do? +

Send Strudel pattern code to the browser REPL for evaluation. The code will be set and evaluated in the Strudel editor. It is categorised as a Execute tool in the Claude DJ MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on play_pattern? +

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

What risk level is play_pattern? +

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

Can I rate-limit play_pattern? +

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

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

play_pattern is provided by the Claude DJ MCP server (uetuluk/claude-dj-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.