OpenRouter Function Calling Overview OpenRouter supports OpenAI-compatible tool/function calling across multiple providers. Define tools as JSON Schema, send them with your request, and the model returns structured instead of free text. This works with GPT-4o, Claude 3.5, Gemini, and other tool-capable models via the same API. The key difference from direct provider APIs: OpenRouter normalizes the tool calling interface, so the same code works across providers. Basic Tool Calling Multi-Turn Tool Loop TypeScript Tool Calling Structured Output (JSON Mode) Model Compatibility | Model | Tool Call…