Test: AI Models Hallucinate Missing Tool Parameters Like Emails

eliobldr · reddit · 2026-08-02

A developer tested 5 models with a meeting booking tool missing required parameters (email and time). Results showed that instead of asking for the missing info, some models flat-out hallucinated fake arguments like [email protected].

The author noted variance across runs and highlighted that cheaper models sometimes outperformed expensive ones. The experiment prompts a discussion on whether developers should guard against hallucinated tool args at the schema level or simply trust the model.

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