IntentMiner: Intent Inversion Attack via Tool Call Analysis in the Model Context Protocol

The rapid evolution of Large Language Models (LLMs) into autonomous agents has led to the adoption of the Model Context Protocol (MCP) as a standard for discovering and invoking external tools. While this architecture decouples the reasoning engine from tool execution to enhance scalability, it introduces a significant privacy surface: third-party MCP servers, acting as semi-honest intermediaries, can observe detailed tool interaction logs outside the user's trusted boundary. In this paper, we first identify and formalize a novel privacy threat termed Intent Inversion, where a semi-honest MCP server attempts to reconstruct the user's private underlying intent solely by analyzing legitimate tool calls. To systematically assess this vulnerability, we propose IntentMiner, a framework that leverages Hierarchical Information Isolation and Three-Dimensional Semantic Analysis, integrating tool purpose, call statements, and returned results, to accurately infer user intent at the step level. Extensive experiments demonstrate that IntentMiner achieves a high degree of semantic alignment (over 85%) with original user queries, significantly outperforming baseline approaches. These results highlight the inherent privacy risks in decoupled agent architectures, revealing that seemingly benign tool execution logs can serve as a potent vector for exposing user secrets.