run_script · Foundry MCP Project MCP: Risk & Policy

WHAT IT DOES

What run_script does on Foundry MCP Project

AI agents invoke run_script to trigger actions in Foundry MCP Project. 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_script needs a policy

This tool executes arbitrary scripts within a Foundry development environment. While not immediately destructive or financial in isolation, script execution in Ethereum development contexts can trigger side effects ranging from state modifications to fund transfers depending on script contents.

From the tool's definition Tool description states 'Runs a script in the current Foundry project.' The verb 'runs' combined with the sibling tools context (cast commands, anvil/chisel startup, contract building) indicates code execution capabilities.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

run_script Rate-limited

run_script 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_script": {
      "limits": [
        {
          "counter": "run_script_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 Foundry MCP Project, so you can run agents against it safely.

FAQ

Questions about run_script

What does the run_script tool do? +

Runs a script in the current Foundry project. It is categorised as a Execute tool in the Foundry MCP Project 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_script? +

Register the Foundry MCP Project MCP server in PolicyLayer and add a rule for run_script: 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 Foundry MCP Project. Nothing to install.

What risk level is run_script? +

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

Can I rate-limit run_script? +

Yes. Add a rate_limit block to the run_script 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_script completely? +

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

run_script is provided by the Foundry MCP Project MCP server (lhemerly/foundry-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.