AI agents use update_merge_request_note 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 modifies existing merge request comments, which is a reversible change (comments can be edited again or deleted separately). It does not delete data, execute code, or move money. It falls squarely into the Write category.
From the tool's definition Tool name 'update_merge_request_note' and description 'Edit a comment on a merge request' indicate modification of existing data. The verb 'Edit' and 'update' confirm this is a write operation that modifies a comment reversibly.
Documented attack patterns abuse exactly the kind of access update_merge_request_note 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 update_merge_request_note:
{
"version": "1",
"default": "deny",
"tools": {
"update_merge_request_note": {
"limits": [
{
"counter": "update_merge_request_note_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_merge_request_note 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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Edit a comment 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 update_merge_request_note: 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.
update_merge_request_note 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 update_merge_request_note 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 update_merge_request_note. 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.
update_merge_request_note 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.