When Neither Side Confirms: Destructive Tool Approval Across MCP Servers and Hosts

Summary

Researchers measured how MCP servers and host applications handle human approval for destructive tool calls, using source code from a 1,000-repository sample of the official MCP registry and 41 open-source hosts and agent SDKs. They found an estimated 90% of destructive tools lack server-side confirmation, and 60.7% of sampled server-application pairs have no enforced human approval by default. In 479 of 960 runs, four of five low-cost models executed an injected deletion through four agent SDKs.

Mitigation

Applications should therefore configure approval. The source estimates that prompting for every tool not annotated read-only or non-destructive would cut the unapproved share of pairs to 5.4%, while universal elicitation support would leave 56.7%.

Topics

• Model Context Protocol

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