The Problem
Your AI generates product descriptions for an e-commerce catalog. Each product has a photo and a text description. You need to verify that descriptions actually match what is in the image — not hallucinate features, colors, or details. You also have a customer service bot that transcribes voicemails. You need to verify transcription accuracy against the original audio.What You Will Learn
- How to pass image URLs to the LLM judge alongside text
- How to auto-generate grading criteria from a short description using
generate_prompt=True - How to compare multiple images (input vs output)
- How to evaluate audio transcriptions
- How the SDK remains backwards-compatible with text-only evaluation
Prerequisites
This cookbook uses Gemini’s native vision and audio capabilities via LiteLLM. The images and audio files used are publicly accessible Google Cloud samples — no additional auth is needed.
Section 1: Image-Text Alignment
Pass animage_url alongside the text output to have the LLM judge evaluate whether the description matches the image.
Accurate Description
Hallucinated Description
Section 2: Auto-Generate Grading Criteria
Instead of writing a detailed rubric, describe what you want to evaluate in plain English and setgenerate_prompt=True. The SDK uses the LLM to generate a proper grading rubric automatically.
Section 3: Comparing Multiple Images
When you need to compare images, useinput_image_url and output_image_url to provide a reference image and a candidate image.
Section 4: Audio Transcription Evaluation
Pass anaudio_url to evaluate transcription accuracy against the original audio.
Section 5: Text-Only Still Works
The multimodal parameters are additive. When you omit image and audio URLs, the judge works exactly as before with text only.Supported Modality Parameters
| Parameter | Description | Example |
|---|---|---|
image_url | Single image for the judge to evaluate | Product photo URL |
input_image_url | Reference/input image for comparison | Original product image |
output_image_url | Output/candidate image for comparison | AI-selected match |
audio_url | Audio file for the judge to listen to | Voicemail recording |
What to Try Next
You have completed all the cookbooks. Here are some directions to explore:Start from the beginning
Revisit local metrics to build a complete validation pipeline combining everything you have learned.
Built-in Evals Reference
Browse the full catalog of 50+ built-in evaluation metrics.