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New tool prevents AI model rug-pulls by hashing tool definitions

A new method called mcp_pin.py has been developed to prevent "MCP tool drift," a security vulnerability where a server modifies a tool's description or inputSchema after a user has approved it. This technique, identified by Invariant Labs and categorized by OWASP as MCP03:2025 Tool Poisoning, involves creating a SHA-256 hash of the tool's definition at the time of approval and re-verifying it before each subsequent use. The solution is implemented in approximately 40 lines of Python code and acts as a CI gate to block potential rug-pull attacks. AI

IMPACT Mitigates a specific supply-chain attack vector targeting AI agents by ensuring tool definitions remain immutable after approval.

RANK_REASON The item describes a specific tool and method for addressing a security vulnerability in AI model interactions, rather than a core AI model release or research paper.

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  1. dev.to — MCP tag TIER_1 English(EN) · Alexey Spinov ·

    MCP Tool Drift: Pin the Manifest, Block Rug-Pulls in 40 Lines

    <p>You approved an MCP tool once. The dialog popped up, you read the description, you clicked yes. Here's the part nobody clicks through to: <strong>that description can change before the next call, and your agent will use the new one without asking again.</strong> Approval is a …