MCP Tool Approval Gaps Allow Destructive Actions
Original title: When Neither Side Confirms: Destructive Tool Approval Across MCP Servers and Hosts
90% of destructive MCP tools lack server-side confirmation and 60.7% of popular host pairs enforce no human approval by default.
LLM agents invoke destructive tools via MCP where human denial is required but split across server and host. 1000-repository sample shows most servers elicit or fallback when host cannot prompt. 41 hosts and SDKs tested; 32 lack default approval. Low-cost models execute injected deletions in 479/960 runs. Full approval would reduce unapproved pairs to 5.4% or 56.7% with universal elicitation.
- 90% destructive tools have no server confirmation
- 32 of 41 hosts lack default approval
- 60.7% of tool-host pairs enforce no approval
- 4/5 low-cost models execute deletions
- Universal elicitation leaves 56.7% unapproved
From the original article
1 min read at arxiv.orgLLM agents call tools that delete data or move money through the Model Context Protocol (MCP). The specification asks for a human who can deny tool calls but splits the mechanism between the server, which can annotate a tool or ask the user through the host (elicitation), and the host application, which decides whether to prompt. We measure both sides from source code.
By Junwei Yao · arxiv.org
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