AI agents call nar_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.
The tool performs analysis of race performance data segmented by popularity/odds ranking for NAR (regional) horse racing. This is a read/query operation with no side effects, data modification, or financial transactions. Similar to the sibling tool 'favorite_performance', it retrieves and aggregates historical race result data.
From the tool's definition 人気別成績を分析 (analyze performance by popularity/odds ranking) — read-only analytical query against NAR regional horse racing data
Documented attack patterns abuse exactly the kind of access nar_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 nar_favorite_performance:
{
"version": "1",
"default": "deny",
"tools": {
"nar_favorite_performance": {}
}
}nar_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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NAR地方競馬の人気別成績を分析. 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 nar_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.
nar_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 nar_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 nar_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.
nar_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.