run_build · Build MCP Server MCP: Risk & Policy

WHAT IT DOES

What run_build does on Build MCP Server

AI agents invoke run_build 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_build needs a policy

This tool executes build commands which are inherently Execute-category actions—they trigger code execution, invoke external processes, and produce side effects (compiled artifacts, generated files, environment changes) that depend on the arguments and build configuration. While not inherently Destructive, build commands can have significant and hard-to-predict effects on the filesystem and development environment.

From the tool's definition Tool description explicitly states 'Run build command in the current directory'. Build commands execute arbitrary build processes that can invoke external tools, compilation, code generation, and environment-dependent operations whose effects depend on the…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

run_build Rate-limited

run_build 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_build": {
      "limits": [
        {
          "counter": "run_build_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_build

What does the run_build tool do? +

Run build command 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_build? +

Register the Build MCP Server MCP server in PolicyLayer and add a rule for run_build: 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_build? +

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

Can I rate-limit run_build? +

Yes. Add a rate_limit block to the run_build 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_build completely? +

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

run_build 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.