create_branch · Supabase MCP Server MCP: Risk & Policy

WHAT IT DOES

What create_branch does on Supabase MCP Server

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

WHY IT NEEDS A POLICY

Why create_branch needs a policy

This tool creates new infrastructure (a development branch with migrations), which modifies the state of the Supabase project. It is a write operation because it creates data/resources, but not destructive because branches are ephemeral and deletable.

From the tool's definition Tool description states it 'Creates a development branch' — the verb 'creates' is a reversible write operation. Branches can be deleted (as evidenced by the sibling tool 'delete_branch'), making this non-destructive.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_branch Rate-limited

create_branch 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": {
    "create_branch": {
      "limits": [
        {
          "counter": "create_branch_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 Supabase MCP Server, so you can run agents against it safely.

FAQ

Questions about create_branch

What does the create_branch tool do? +

Creates a development branch with migrations from production branch. It is categorised as a Write tool in the Supabase 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 create_branch? +

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

What risk level is create_branch? +

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

Can I rate-limit create_branch? +

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

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

create_branch is provided by the Supabase MCP Server MCP server (pipethedev/supabase-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.