debug_evaluate_watches · Polybugger MCP: Risk & Policy

WHAT IT DOES

What debug_evaluate_watches does on Polybugger

AI agents invoke debug_evaluate_watches to trigger actions in Polybugger. 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 debug_evaluate_watches needs a policy

Watch expression evaluation runs arbitrary expressions in the debugged process's context, which constitutes code execution. While read-like in intent (returning results), the act of evaluating expressions can trigger side effects in the target program depending on what expressions are watched.

From the tool's definition 'Evaluate all watch expressions and return results' — evaluating expressions executes code in the context of a running debug session

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

debug_evaluate_watches Rate-limited

debug_evaluate_watches 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": {
    "debug_evaluate_watches": {
      "limits": [
        {
          "counter": "debug_evaluate_watches_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 Polybugger, so you can run agents against it safely.

FAQ

Questions about debug_evaluate_watches

What does the debug_evaluate_watches tool do? +

Evaluate all watch expressions and return results. It is categorised as a Execute tool in the Polybugger MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on debug_evaluate_watches? +

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

What risk level is debug_evaluate_watches? +

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

Can I rate-limit debug_evaluate_watches? +

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

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

debug_evaluate_watches is provided by the Polybugger MCP server (wilfoa/polybugger-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.