AI agents call favorite_performance to retrieve information from JVLink MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool analyzes/queries historical race performance data for horses based on their odds ranking. It retrieves and aggregates existing data without any write, execute, or destructive side effects. Severity is low as it only reads race statistics.
From the tool's definition 指定した人気順位の馬の成績を分析 (Analyzes performance of horses at specified popularity rankings)
Documented attack patterns abuse exactly the kind of access favorite_performance gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and JVLink MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for favorite_performance:
{
"version": "1",
"default": "deny",
"tools": {
"favorite_performance": {}
}
}favorite_performance is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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指定した人気順位の馬の成績を分析. It is categorised as a Read tool in the JVLink MCP Server MCP Server, which means it retrieves data without modifying state.
Register the JVLink MCP Server MCP server in PolicyLayer and add a rule for favorite_performance: 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 JVLink MCP Server. Nothing to install.
favorite_performance 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 favorite_performance 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 favorite_performance. 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.
favorite_performance is provided by the JVLink MCP Server MCP server (miyamamoto/jvlink-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from JVLink MCP Server, 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.
25 JVLink MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.