AI agents call cache_stats to retrieve information from Crossref Local without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves informational statistics about an internal cache. It has no side effects, does not execute code or external operations, does not modify data, and does not delete or perform financial transactions. It is a straightforward read operation with minimal blast radius—at worst, an agent could learn cache structure details, which poses negligible risk.
From the tool's definition Tool name 'cache_stats' and description 'Get cache statistics' indicate a query operation that retrieves metadata about cache state without modifying, executing operations, or deleting data.
Documented attack patterns abuse exactly the kind of access cache_stats gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Crossref Local, and nothing reaches the server without passing your rules. This is the rule we recommend for cache_stats:
{
"version": "1",
"default": "deny",
"tools": {
"cache_stats": {}
}
}cache_stats is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get cache statistics. It is categorised as a Read tool in the Crossref Local MCP Server, which means it retrieves data without modifying state.
Register the Crossref Local MCP server in PolicyLayer and add a rule for cache_stats: 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 Crossref Local. Nothing to install.
cache_stats 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 cache_stats 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 cache_stats. 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.
cache_stats is provided by the Crossref Local MCP server (ywatanabe1989/crossref-local). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Crossref Local, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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17 Crossref Local tools catalogued and risk-classified — across an index of 43,000+ MCP servers.