ModelFusion is a toolkit for developers and advanced users working with LLMs. It’s designed to help you plan AI spend, choose the right model for a task, and improve prompt quality without heavy manual analysis.
Cost calculators and model comparison
ModelFusion provides API cost calculators and side-by-side comparisons across many models, helping you estimate budgets and pick a cost-effective option for a product or experiment.
- Cost calculators for GPT-4, Claude, Gemini, LLaMA, Mistral, and more
- Budget estimation and pricing comparisons across models
- Model selection support based on cost and intended use
Prompt library, optimization, and observability
Along with a prompt library, ModelFusion includes tools to test and refine prompt wording, compare outputs, and select the best-performing prompts for a specific model and task. It also supports both cloud and locally hosted models with basic observability.
- Prompt templates and prompt optimization workflows
- A/B-style testing of prompt variations and results
- Request tracking, metrics, and model behavior monitoring

