AI agents call lean_leandex to retrieve information from Lean Lsp without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Given the context of an LSP (Language Server Protocol) server for Lean theorem prover, 'lean_leandex' most likely retrieves documentation or definitions (a 'dex' typically refers to an index or directory). Like sibling tools that fetch file outlines, completions, and diagnostic information, this appears to be a read-only query tool.
From the tool's definition Tool name 'lean_leandex' and sibling tools like 'file_outline', 'lean_completions', 'lean_declaration_file', 'lean_diagnostic_messages', and 'lean_file_contents' all suggest information retrieval operations.
Documented attack patterns abuse exactly the kind of access lean_leandex gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Lean Lsp, and nothing reaches the server without passing your rules. This is the rule we recommend for lean_leandex:
{
"version": "1",
"default": "deny",
"tools": {
"lean_leandex": {}
}
}lean_leandex is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
Free to start. No card required.
lean_leandex. It is categorised as a Read tool in the Lean Lsp MCP Server, which means it retrieves data without modifying state.
Register the Lean Lsp MCP server in PolicyLayer and add a rule for lean_leandex: 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 Lean Lsp. Nothing to install.
lean_leandex 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 lean_leandex 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 lean_leandex. 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.
lean_leandex is provided by the Lean Lsp MCP server (project-numina/lean-lsp-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Lean Lsp, 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.
22 Lean Lsp tools catalogued and risk-classified — across an index of 43,000+ MCP servers.