AI agents use create_branch to create or update resources in Gitlab — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Gitlab environment.
Creating a branch is a reversible modification to a repository's state. It adds a new reference but does not delete data or execute arbitrary code. An AI agent misusing this tool could create many branches (polluting the repository) or create branches with names that interfere with CI/CD pipelines, but the impact is recoverable and localized to branch management. This justifies 'medium' severity rather than 'high'.
From the tool's definition Tool name 'create_branch' and description 'Create a new branch in a GitLab project' directly indicate creating new data (a branch) in a repository, which is a reversible write operation.
Documented attack patterns abuse exactly the kind of access create_branch gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Gitlab, and nothing reaches the server without passing your rules. This is the rule we recommend for create_branch:
{
"version": "1",
"default": "deny",
"tools": {
"create_branch": {
"limits": [
{
"counter": "create_branch_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}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.
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Create a new branch in a GitLab project. It is categorised as a Write tool in the Gitlab MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
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. Nothing to install.
create_branch is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
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.
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.
create_branch is provided by the Gitlab MCP server (yoda-digital/mcp-gitlab-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 88 Gitlab tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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88 Gitlab tools catalogued and risk-classified — across an index of 42,500+ MCP servers.