lerna · Cargo MCP: Risk & Policy

WHAT IT DOES

What lerna does on Cargo

AI agents invoke lerna to trigger actions in Cargo. 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 lerna needs a policy

Lerna is a monorepo management tool that executes package management operations. The 'run' command executes arbitrary scripts defined in package.json files, and the 'version' command modifies package.json files and can trigger lifecycle hooks. While 'list' and 'changed' are read-only queries, the tool's primary capability is executing commands whose side effects depend on what scripts are configured.

From the tool's definition Tool description states it 'Runs Lerna monorepo commands' which executes external operations. Lerna commands like 'run' and 'version' can trigger arbitrary scripts and modify package versions across a monorepo, with effects dependent on arguments.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

lerna Rate-limited

lerna 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": {
    "lerna": {
      "limits": [
        {
          "counter": "lerna_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 Cargo, so you can run agents against it safely.

FAQ

Questions about lerna

What does the lerna tool do? +

Runs Lerna monorepo commands (list, run, changed, version) and returns structured package information. It is categorised as a Execute tool in the Cargo MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on lerna? +

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

What risk level is lerna? +

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

Can I rate-limit lerna? +

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

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

lerna is provided by the Cargo MCP server (Dave-London/Pare). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.