AI agents call search_features 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 searches or filters available features/columns in the JRA-VAN database based on keyword input. It returns matching feature definitions without executing queries on race data itself, modifying any data, or triggering external operations. This is a classic Read operation - information retrieval with no side effects.
From the tool's definition Tool name 'search_features' and description 'キーワードで特徴量を検索' (search features by keyword) indicates a query/search operation that retrieves feature metadata.
Documented attack patterns abuse exactly the kind of access search_features 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 search_features:
{
"version": "1",
"default": "deny",
"tools": {
"search_features": {}
}
}search_features is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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キーワードで特徴量を検索. 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 search_features: 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.
search_features 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 search_features 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 search_features. 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.
search_features 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.
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25 JVLink MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.