How AI Tool Calling Works: Models Request Data, Your Code Executes It

AI language models cannot access live data on their own because their knowledge is frozen at a training cutoff date, making real-time information like weather or current prices unavailable. Tool calling is a mechanism that bridges this gap by allowing models to issue structured requests for external data, which the surrounding application code then fulfills. When a user asks a question requiring live data, the model responds with a formatted instruction — such as 'call get_weather for Toronto' — rather than executing any code itself. The application runs the actual function, retrieves the result, and passes it back to the model, which then formulates a final answer grounded in real-world data. A developer tutorial published on DEV Community demonstrates this workflow using Amazon Bedrock's Converse API with Claude, showing single-tool, multi-tool, and context-injection approaches via open-source example scripts.