start_turn · Cursor Otel MCP: Risk & Policy

WHAT IT DOES

What start_turn does on Cursor Otel

AI agents use start_turn to create or update resources in Cursor Otel — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Cursor Otel environment.

WHY IT NEEDS A POLICY

Why start_turn needs a policy

This tool creates a new OpenTelemetry trace entry at the start of each agent turn. It writes telemetry/observability data but has no destructive, financial, or execution side effects. Misuse would result in spurious trace records at worst, making severity low.

From the tool's definition 'Start an OpenTelemetry trace for an agent turn' — creates a new telemetry trace/span record

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

start_turn Rate-limited

start_turn 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about start_turn

What does the start_turn tool do? +

Start an OpenTelemetry trace for an agent turn. Call at the beginning of handling each user query. It is categorised as a Write tool in the Cursor Otel MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on start_turn? +

Register the Cursor Otel MCP server in PolicyLayer and add a rule for start_turn: 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 Cursor Otel. Nothing to install.

What risk level is start_turn? +

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

Can I rate-limit start_turn? +

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

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

start_turn is provided by the Cursor Otel MCP server (smith/cursor-otel). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.