Function Calling

Webisoft AI team Updated 2 min read

Function calling, also called tool use, is the mechanism by which an AI model requests that external software run a specific action on its behalf, such as looking up an order, querying a database, or sending an email, and then incorporates the result into its response. The model itself never executes anything: it outputs a structured request (“call get_order_status with order_id 4821”), your application runs the actual function, returns the result, and the model continues with real data in hand.

The flow: developers describe available functions to the model (name, purpose, parameters); the model decides when a user’s request needs one; it emits the call as structured output; the application executes and returns results; the model answers. Chained together in a loop, call, observe, decide, call again, function calling is the engine that turns a chat model into an AI agent. Standards like the Model Context Protocol exist to make the tools themselves plug-and-play across AI applications.

The control point is important: because your code executes every call, your code decides what’s allowed, which functions exist, with what permissions, and which actions require human confirmation before running.

Why it matters at work

Function calling is where AI stops being a writing assistant and starts being a doing assistant. Without it, a model can only tell a customer how to check their order status; with it, the model checks the actual order and answers. It’s also the design surface for safety: exposing read_customer_record is a very different risk decision than exposing issue_refund, and well-built systems keep destructive actions behind confirmation steps and audit logs.

A work example

A support assistant receives “Where’s my order?”, calls the order_lookup function with the customer’s ID, gets back “shipped Tuesday, arriving Friday” from the live system, and replies with the real tracking status, no hand-off, no guessing.

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FAQ

Does function calling mean the model runs code itself? No. The model outputs a structured request naming the function and its arguments; your application decides whether to execute it and returns the result to the model.

Why is function calling important for AI at work? It is how a language model gets from talking to doing: looking up live data, querying internal systems, or triggering actions. Without it, a model only knows what is in its training data and prompt.