3 Patterns That Fix LLM API Calling (Stop Getting Hallucinated Parameters)

LLMs frequently fail at API tool calling due to hallucinated parameter names, wrong nesting depths, and dropped required fields when schemas are deeply nested. The article presents three patterns to improve reliability from ~60% to 95%+, with the primary fix being flattening nested parameter schemas into single-depth dot-notation keys so the model doesn't have to track multiple nesting levels. A Python transform function reconstructs the nested structure in middleware before sending to the actual API.