pr_cancel · Pr Review MCP: Risk & Policy

WHAT IT DOES

What pr_cancel does on Pr Review

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

WHY IT NEEDS A POLICY

Why pr_cancel needs a policy

This tool cancels an active review process, which is a reversible state change (the review could presumably be re-invoked). It modifies the state of a running invocation but does not delete data permanently, execute arbitrary code, or involve financial transactions. The blast radius is medium since canceling a review mid-process could disrupt the review workflow for a PR.

From the tool's definition Cancel an active review invocation, preventing further polling

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

pr_cancel Rate-limited

pr_cancel 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": {
    "pr_cancel": {
      "limits": [
        {
          "counter": "pr_cancel_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 Pr Review, so you can run agents against it safely.

FAQ

Questions about pr_cancel

What does the pr_cancel tool do? +

Cancel an active review invocation, preventing further polling. Provide either invocationId (from pr_invoke or pr_sessions) or (owner, repo, pr) to cancel the most recent active invocation for that PR. It is categorised as a Write tool in the Pr Review MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on pr_cancel? +

Register the Pr Review MCP server in PolicyLayer and add a rule for pr_cancel: 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 Pr Review. Nothing to install.

What risk level is pr_cancel? +

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

Can I rate-limit pr_cancel? +

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

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

pr_cancel is provided by the Pr Review MCP server (thebtf/pr-review-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.