Create a new discussion on a merge request
AI agents use create_merge_request_discussion 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.
This tool creates new discussion content on a merge request, which is a reversible write operation. It modifies state by adding a discussion but does not delete data, execute arbitrary code, or commit financial obligations.
From the tool's definition Tool name and description: 'create_merge_request_discussion' - 'Create a new discussion on a merge request'. The verb 'create' indicates a write operation that adds new data to the system.
Documented attack patterns abuse exactly the kind of access create_merge_request_discussion 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_merge_request_discussion:
{
"version": "1",
"default": "deny",
"tools": {
"create_merge_request_discussion": {
"limits": [
{
"counter": "create_merge_request_discussion_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}create_merge_request_discussion 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 discussion on a merge request. 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_merge_request_discussion: 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_merge_request_discussion 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_merge_request_discussion 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_merge_request_discussion. 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_merge_request_discussion 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.