mysql_cross_host_query · MySQL MCP Server MCP: Risk & Policy

WHAT IT DOES

What mysql_cross_host_query does on MySQL MCP Server

AI agents invoke mysql_cross_host_query to trigger actions in MySQL MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why mysql_cross_host_query needs a policy

This tool executes SQL queries across multiple MySQL hosts. While described in an analytics context, executing arbitrary queries across multiple database systems carries high risk: it could include data-modifying or destructive SQL (UPDATE, DELETE, DROP), expose sensitive data from multiple systems simultaneously, and the cross-host nature multiplies the blast radius significantly.

From the tool's definition "Execute queries across multiple MySQL hosts" — the tool runs queries across multiple database systems and combines results

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mysql_cross_host_query Rate-limited

mysql_cross_host_query stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "mysql_cross_host_query": {
      "limits": [
        {
          "counter": "mysql_cross_host_query_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches MySQL MCP Server, so you can run agents against it safely.

FAQ

Questions about mysql_cross_host_query

What does the mysql_cross_host_query tool do? +

Execute queries across multiple MySQL hosts and combine results for comprehensive analysis. It is categorised as a Execute tool in the MySQL MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on mysql_cross_host_query? +

Register the MySQL MCP Server MCP server in PolicyLayer and add a rule for mysql_cross_host_query: 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 MySQL MCP Server. Nothing to install.

What risk level is mysql_cross_host_query? +

mysql_cross_host_query is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit mysql_cross_host_query? +

Yes. Add a rate_limit block to the mysql_cross_host_query 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.

How do I block mysql_cross_host_query completely? +

Set action: deny in the PolicyLayer policy for mysql_cross_host_query. 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.

What MCP server provides mysql_cross_host_query? +

mysql_cross_host_query is provided by the MySQL MCP Server MCP server (ttpears/mysql-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.