What Code to Change When Switching LLM APIs: Three Must-Change Configs and Four Compatibility Checks

When staying on the OpenAI-compatible protocol, switching models usually requires changing only base_url, api_key, and model—but if your code uses length parameters, sampling parameters, streaming usage, tool calling, or structured outputs, verify each against the target model.

How to Write a Tool Calling API? Four-Layer Cross-Model Differences and the Loop Skeleton

This article provides a portable tool calling loop skeleton, breaking down four layers of differences across models: function declarations, trigger control, return structure, and multi-step termination, along with adapter design, verification methods, and a regression checklist.