run_test · Build MCP Server MCP: Risk & Policy

WHAT IT DOES

What run_test does on Build MCP Server

AI agents invoke run_test to trigger actions in Build MCP Server. 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 run_test needs a policy

This tool executes test suites, which are external operations whose effects depend on what tests do (they may modify filesystem state, call external services, or trigger side effects). The blast radius is high because a malicious test suite or uncontrolled test execution could compromise the development environment.

From the tool's definition Tool name 'run_test' combined with description 'Run tests in the current directory' explicitly indicates execution of arbitrary test commands. Server description confirms it 'running build commands, executing tests' as core functionality.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

run_test Rate-limited

run_test 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": {
    "run_test": {
      "limits": [
        {
          "counter": "run_test_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 Build MCP Server, so you can run agents against it safely.

FAQ

Questions about run_test

What does the run_test tool do? +

Run tests in the current directory. It is categorised as a Execute tool in the Build MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on run_test? +

Register the Build MCP Server MCP server in PolicyLayer and add a rule for run_test: 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 Build MCP Server. Nothing to install.

What risk level is run_test? +

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

Can I rate-limit run_test? +

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

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

run_test is provided by the Build MCP Server MCP server (teodortrotea/mcptest). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.