create_branch · GitLab MCP: Risk & Policy

WHAT IT DOES

What create_branch does on GitLab MCP

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

WHY IT NEEDS A POLICY

Why create_branch needs a policy

Creating a branch is a write operation that adds new data to the repository. While reversible via branch deletion, misuse could enable an attacker to pollute the repository with malicious branches, create branches for unauthorized changes, or trigger CI/CD pipelines on those branches.

From the tool's definition The tool description states it 'Create[s] branch from ref', which is a creation operation that modifies the repository state. The action is reversible (branches can be deleted), and it does not execute code, delete data irreversibly, or move money.

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 GitLab MCP, so you can run agents against it safely.

FAQ

Questions about create_branch

What does the create_branch tool do? +

Create branch from ref (an existing branch name, tag, or commit SHA). It is categorised as a Write tool in the GitLab MCP 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 GitLab 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 GitLab MCP. 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 GitLab MCP server (shahabmosavi/gitlab_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.