Return trials located at the Pareto front in the study.
AI agents call best_trials to retrieve information from Optuna MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and returns information about trials that represent optimal trade-offs (Pareto front) in an optimization study. It performs a read-only query operation with no side effects—it does not create, modify, delete, or execute any external operations. The action is informational only, analyzing already-computed results from the study.
From the tool's definition Tool name 'best_trials' and description 'Return trials located at the Pareto front in the study' indicate retrieval and analysis of existing optimization results with no modification or deletion of data.
Documented attack patterns abuse exactly the kind of access best_trials gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Optuna MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for best_trials:
{
"version": "1",
"default": "deny",
"tools": {
"best_trials": {}
}
}best_trials is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Return trials located at the Pareto front in the study. It is categorised as a Read tool in the Optuna MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Optuna MCP Server MCP server in PolicyLayer and add a rule for best_trials: 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 Optuna MCP Server. Nothing to install.
best_trials 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 best_trials 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 best_trials. 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.
best_trials is provided by the Optuna MCP Server MCP server (optuna/optuna-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 26 Optuna MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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26 Optuna MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.