How to Intercept Hallucinated LLM Tool Calls

9ThisUsernameIsTaken · reddit · 2026-07-14

The author connected an agent to internal APIs and custom tools, but twice a day it "invents" non-existent tool calls—either hitting non-existent endpoints or fabricating parameters outside the schema.

The problem is that logs typically only show generic timeouts or deep stack errors, making it hard to quickly tell if a tool genuinely failed or if the model hallucinated the call.

They are looking for an interception/validation layer between the model's output and the execution layer to identify and flag non-existent tools or illegal parameters before execution. This would specifically catch hallucinated tool calls, going beyond standard observability metrics like latency and token stats.

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