Show global variables.
AI agents call show_global_variables to retrieve information from Mysql without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries and displays MySQL global variables (configuration parameters like max_connections, timeout values, etc.). It has no side effects, does not modify state, and is consistent with the server's advertised read-only monitoring capabilities. The low severity reflects minimal risk even if misused by an agent, as viewing configuration poses no data loss or operational harm.
From the tool's definition Tool name 'show_global_variables' and server description emphasizing 'read-only queries' and 'server monitoring' indicate this retrieves configuration data without modification. The verb 'show' is a pure read operation in MySQL context.
Documented attack patterns abuse exactly the kind of access show_global_variables gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Mysql, and nothing reaches the server without passing your rules. This is the rule we recommend for show_global_variables:
{
"version": "1",
"default": "deny",
"tools": {
"show_global_variables": {}
}
}show_global_variables is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Show global variables. It is categorised as a Read tool in the Mysql MCP Server, which means it retrieves data without modifying state.
Register the Mysql MCP server in PolicyLayer and add a rule for show_global_variables: 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. Nothing to install.
show_global_variables 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 show_global_variables 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 show_global_variables. 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.
show_global_variables is provided by the Mysql MCP server (mukul975/mysql-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Mysql, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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233 Mysql tools catalogued and risk-classified — across an index of 43,000+ MCP servers.