---
title: "Comment by Varsha on \"One Does Not Simply read_file('/etc/passwd') — Argument Policies Land in Heimdall MCP\" | Hashnode"
description: "This is exactly the kind of MCP security issue people overlook. Tool access is powerful, but argument level controls matter just as much. It’s not enough to say"
url: "https://hashnode.com/posts/one-does-not-simply-read-file-etc-passwd-argument-policies-land-in-heimdall-mcp/6a159eccda253d50d4b49838/comment/6a16e46ebadcd8afcbec7d07"
---

[Discussion](https://hashnode.com/posts/one-does-not-simply-read-file-etc-passwd-argument-policies-land-in-heimdall-mcp/6a159eccda253d50d4b49838)

Comment [One Does Not Simply read\_file('/etc/passwd') — Argument Policies Land in Heimdall MCP](https://hashnode.com/posts/one-does-not-simply-read-file-etc-passwd-argument-policies-land-in-heimdall-mcp/6a159eccda253d50d4b49838)

[Varsha](https://hashnode.com/@varsha23)

[May 27](https://hashnode.com/posts/one-does-not-simply-read-file-etc-passwd-argument-policies-land-in-heimdall-mcp/6a159eccda253d50d4b49838/comment/6a16e46ebadcd8afcbec7d07)

This is exactly the kind of MCP security issue people overlook. Tool access is powerful, but argument level controls matter just as much. It’s not enough to say “this tool is allowed.” The system also needs to know what inputs should never pass through.