init · Jj MCP: Risk & Policy

WHAT IT DOES

What init does on Jj

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

WHY IT NEEDS A POLICY

Why init needs a policy

This tool creates new repositories and can initialize git repos, which are write operations that create data but are reversible (a repository can be deleted). It does not execute arbitrary commands, delete data irreversibly, or move money.

From the tool's definition The tool description states it will 'Create a new Jujutsu (jj) repository backed by a Git repo' and 'Can create a new Git repo or import an existing one.' The verb 'Create' and the action of initializing a new repository with potential git repo…

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

init Rate-limited

init 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": {
    "init": {
      "limits": [
        {
          "counter": "init_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 Jj, so you can run agents against it safely.

FAQ

Questions about init

What does the init tool do? +

Create a new Jujutsu (jj) repository backed by a Git repo. Can create a new Git repo or import an existing one. Parameters: destination (Optional destination directory), colocate (Optional flag to colocate the jj repo with the git repo), gitRepo (Optional path to existing git repo to use). It is categorised as a Write tool in the Jj MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on init? +

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

What risk level is init? +

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

Can I rate-limit init? +

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

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

init is provided by the Jj MCP server (jj-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.