AI agents invoke cancel_query to trigger actions in Trino 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.
Cancelling a running query is an operational action that interrupts an external process (a distributed SQL query on Trino). It is not purely reading data, nor does it delete/overwrite stored data. It triggers an external operation (query cancellation) whose effect depends on which query ID is supplied.
From the tool's definition 'Cancel a running query' — terminates an in-flight execution on the Trino engine
Documented attack patterns abuse exactly the kind of access cancel_query gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Trino MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for cancel_query:
{
"version": "1",
"default": "deny",
"tools": {
"cancel_query": {
"limits": [
{
"counter": "cancel_query_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}cancel_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.
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Cancel a running query. It is categorised as a Execute tool in the Trino MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Trino MCP Server MCP server in PolicyLayer and add a rule for cancel_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 Trino MCP Server. Nothing to install.
cancel_query 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 cancel_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.
Set action: deny in the PolicyLayer policy for cancel_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.
cancel_query is provided by the Trino MCP Server MCP server (stinkgen/trino_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Trino MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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3 Trino MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.