Show open tables in the table cache.
AI agents call show_open_tables 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 internal MySQL table cache state and returns information only. It performs no modifications, deletions, or external operations. The verb 'show' combined with the informational nature of displaying cache contents classifies it as a Read operation with low severity—an AI agent querying this poses minimal risk.
From the tool's definition Tool name 'show_open_tables' and description 'Show open tables in the table cache' indicate a read-only query operation that retrieves cache status without modifying data.
Documented attack patterns abuse exactly the kind of access show_open_tables 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_open_tables:
{
"version": "1",
"default": "deny",
"tools": {
"show_open_tables": {}
}
}show_open_tables is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Show open tables in the table cache. 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_open_tables: 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_open_tables 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_open_tables 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_open_tables. 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_open_tables 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.