AI agents use add_user_to_group to create or update resources in Prometheus MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Prometheus MCP Server environment.
Adding a user to a group modifies access control and permissions, which is a reversible Write operation. However, the blast radius is high because incorrect group assignments could grant unintended access to AWS resources or data. Confidence is moderate (0.7) due to empty description—it could theoretically be more severe if the tool also modifies policies or roles, but the name suggests a simple membership change.
From the tool's definition Tool name 'add_user_to_group' directly indicates group membership modification. The sibling tools include 'add_inline_policy' and 'add_attachments_to_set', showing this server performs mutation operations. No description provided to clarify scope.
Documented attack patterns abuse exactly the kind of access add_user_to_group gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Prometheus MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for add_user_to_group:
{
"version": "1",
"default": "deny",
"tools": {
"add_user_to_group": {
"limits": [
{
"counter": "add_user_to_group_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_user_to_group 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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add_user_to_group. It is categorised as a Write tool in the Prometheus MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Prometheus MCP Server MCP server in PolicyLayer and add a rule for add_user_to_group: 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 Prometheus MCP Server. Nothing to install.
add_user_to_group 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 add_user_to_group 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 add_user_to_group. 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.
add_user_to_group is provided by the Prometheus MCP Server MCP server (awslabs.prometheus-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Prometheus MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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805 Prometheus MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.