faber_create_stack · Faber MCP Server MCP: Risk & Policy

WHAT IT DOES

What faber_create_stack does on Faber MCP Server

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

WHY IT NEEDS A POLICY

Why faber_create_stack needs a policy

This tool creates multiple resources (application, domain, database, SSL certificate, environment configuration) in a coordinated fashion. While it provisions significant infrastructure, these actions are generally reversible (resources can be deleted/torn down), placing it in Write rather than Destructive.

From the tool's definition Create a full application stack (app + domain + database + SSL + .env). Handles GitHub Device Flow OAuth for automatic deploy key setup if configured on server.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

faber_create_stack Rate-limited

faber_create_stack 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": {
    "faber_create_stack": {
      "limits": [
        {
          "counter": "faber_create_stack_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 Faber MCP Server, so you can run agents against it safely.

FAQ

Questions about faber_create_stack

What does the faber_create_stack tool do? +

Create a full application stack (app + domain + database + SSL + .env). Handles GitHub Device Flow OAuth for automatic deploy key setup if configured on server. First call shows a preview - set confirm: true to execute. It is categorised as a Write tool in the Faber MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on faber_create_stack? +

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

What risk level is faber_create_stack? +

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

Can I rate-limit faber_create_stack? +

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

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

faber_create_stack is provided by the Faber MCP Server MCP server (joshtrebilco/faber-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.