AI agents call cache_version 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.
This is a straightforward information retrieval operation. Getting version information is a read-only action with no side effects, no code execution, no data modification, and no destructive operations. The blast radius of misuse is minimal—an AI agent could only learn version details, which has limited security impact. This clearly falls under the 'Read' category.
From the tool's definition Tool name 'cache_version' and description 'Get the version of the cache server' indicate a query operation that retrieves version information without modifying any data or triggering external operations.
Documented attack patterns abuse exactly the kind of access cache_version 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 cache_version:
{
"version": "1",
"default": "deny",
"tools": {
"cache_version": {}
}
}cache_version is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get the version of the cache server. 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 cache_version: 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.
cache_version 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 cache_version 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 cache_version. 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.
cache_version 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.