Set a MySQL variable.
AI agents invoke mysql_set_variable to trigger actions in Mysql. 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.
Setting MySQL variables (e.g., global variables like max_connections, sql_mode, innodb_buffer_pool_size) alters server or session behavior at runtime. This is not a simple data write but an execution of a configuration change that can affect all connections, query behavior, security settings, or performance characteristics.
From the tool's definition 'Set a MySQL variable' — modifies runtime server configuration/session state in MySQL
Documented attack patterns abuse exactly the kind of access mysql_set_variable 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 mysql_set_variable:
{
"version": "1",
"default": "deny",
"tools": {
"mysql_set_variable": {
"limits": [
{
"counter": "mysql_set_variable_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}mysql_set_variable 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.
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Set a MySQL variable. It is categorised as a Execute tool in the Mysql MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Mysql MCP server in PolicyLayer and add a rule for mysql_set_variable: 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.
mysql_set_variable is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the mysql_set_variable 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 mysql_set_variable. 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.
mysql_set_variable 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.
Free to start. No card required.
233 Mysql tools catalogued and risk-classified — across an index of 43,000+ MCP servers.