Free AI Function Calling Tester - Test LLM Tool Use Online

AI Function Calling Tester - What Can It Do?

Free online AI Function Calling Tester. Test and debug LLM Function Calling / Tool Use capabilities. Define tool schemas, simulate calls, and validate parameter extraction. Supports OpenAI and Anthropic formats.

Key Features

• Dual Format Support: supports both OpenAI and Anthropic Tool Use formats
• Schema Generation: automatically generates standard tool schemas from your parameter definition
• Call Simulation: simulate LLM function call responses to test parameter extraction
• Schema Validation: validate parameter schema completeness and correctness
• One-click Export: generate JSON config for direct use in API calls
• Practical Testing: enter a user message and view the simulated function call result

How to Use

1. Configure Parameters: set tool parameters based on your needs
2. Generate Result: click the generate button to get the schema
3. Copy and Use: copy the result and use it in your application

Use Cases

• Tool Development: build and test LLM function calling tool definitions
• API Debugging: debug OpenAI/Anthropic Function Calling interfaces
• Parameter Validation: validate tool parameter schemas against your spec
• Demonstration: show how LLM function calling works

Learn More

Function Calling is a technique that lets LLMs interact with external tools. OpenAI introduced Function Calling in June 2023, and Anthropic later added Tool Use. The formats differ: OpenAI uses the function and parameters fields, while Anthropic uses input_schema. In 2024-2026, MCP (Model Context Protocol) is becoming the standard for tool definitions, making tools work across platforms.