AI agents call list_databases to retrieve information from MCP ClickHouse without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a simple enumeration of existing databases—a read-only operation with no capability to modify, delete, or execute code. The blast radius of misuse is minimal; an attacker gains only informational access to database names. Severity is low as this represents basic reconnaissance with no destructive or operational impact.
From the tool's definition Tool name 'list_databases' and description 'List available ClickHouse databases' indicate a query operation that retrieves metadata with no modification or side effects.
Documented attack patterns abuse exactly the kind of access list_databases gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP ClickHouse, and nothing reaches the server without passing your rules. This is the rule we recommend for list_databases:
{
"version": "1",
"default": "deny",
"tools": {
"list_databases": {}
}
}list_databases is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List available ClickHouse databases. It is categorised as a Read tool in the MCP ClickHouse MCP Server, which means it retrieves data without modifying state.
Register the MCP ClickHouse MCP server in PolicyLayer and add a rule for list_databases: 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 MCP ClickHouse. Nothing to install.
list_databases 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_databases 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_databases. 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_databases is provided by the MCP ClickHouse MCP server (oualib/chmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from MCP ClickHouse, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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55 MCP ClickHouse tools catalogued and risk-classified — across an index of 43,000+ MCP servers.