AI agents call list-custom-line-items to retrieve information from Prometheus MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The 'list' prefix strongly indicates a retrieval operation that queries and returns custom line items without modifying, executing external operations, or deleting data. Given the naming convention and context of a Prometheus/AWS management server, this most likely retrieves billing or metric line items. The Read category is appropriate, with low severity due to the non-mutative nature of list operations.
From the tool's definition Tool name 'list-custom-line-items' uses the 'list' verb, which typically retrieves or queries data without side effects. The empty description limits full certainty of its exact behavior.
Documented attack patterns abuse exactly the kind of access list-custom-line-items 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 list-custom-line-items:
{
"version": "1",
"default": "deny",
"tools": {
"list-custom-line-items": {}
}
}list-custom-line-items is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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list-custom-line-items. It is categorised as a Read tool in the Prometheus MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Prometheus MCP Server MCP server in PolicyLayer and add a rule for list-custom-line-items: 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.
list-custom-line-items is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list-custom-line-items 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 list-custom-line-items. 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.
list-custom-line-items 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.