How to Prevent Wrong Function Calls and Parameter Hallucination in OpenAI
Stop GPT-4o and Claude from inventing missing arguments or calling the wrong endpoint.
OpenAI models hallucinate function arguments when required details are absent from context. Exogram intercepts tool calls before execution, verifying that arguments match existing entity states and schema definitions rather than fabricated values.
What Actually Happened in the Real World
An automated scheduling agent was asked to reschedule an appointment. The user did not specify the appointment ID. Instead of asking for clarification, GPT-4 invented an ID (APT-1001) and cancelled another customer's reservation.
Why Polite Prompts Like “Please Don't Do This” Fail
Models are biased toward taking action. When an argument is marked optional or ambiguous in the schema, the model frequently guesses rather than pausing.
The Sub-Millisecond Code Fix
Exogram verifies entity existence in the local ledger. If the proposed ID does not match an authenticated record owned by that user, the call is blocked immediately.
from exogram import Exogram
exo = Exogram()
def handle_cancel(appointment_id: str, user_id: str):
# Verify entity exists and belongs to this user
exo.verify_entity_ownership(entity_id=appointment_id, owner_id=user_id)
return db.cancel_appointment(appointment_id)Frequently Asked Questions
Does Exogram require calling another LLM to verify arguments?
No. Exogram uses fast deterministic checks against your database and rules engine in under 0.07ms.
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Stop AI Mistakes Before They Execute
Exogram sits directly between your AI model and your tools. Set up in 10 seconds inside Claude, Cursor, ChatGPT, or your own code.