What is function calling? Model-generated arguments versus program execution
Understand declarations, argument validation, call identifiers, and result returns through an order-status lookup, distinguishing requested actions from confirmed execution.
Understand the concept
Function calling lets a model generate a function name and structured arguments from application-provided definitions. The application decides whether to execute and returns results. A call request is not external execution. Schema validity does not establish semantic correctness or authorization; programs must validate identity, scope, errors, and duplicates.
Function definitions describe actions and arguments
An order lookup may require order_id, extracted from a user message. Define field meaning and missing-data behavior rather than only a vague function name. Ask for a missing ID or use authorized context instead of inventing one.
OpenAI and Google expose function calling with different fields and automation. Determine whether the SDK or application executes a function. Hosted tools differ from local functions that the application must run.
Validate business meaning as well as data types
A string ID can still belong to another user. Verify access scope rather than treating model selection as authorization. Separate read and write permissions instead of exposing unnecessary modifications through a broad management function.
Schemas can reduce missing fields and type errors but do not establish sensible actions. A valid date can still use the wrong month. Return explicit validation failures for correction or stopping rather than silently substituting defaults.
Match returned results to the original calls
Multiple calls need matching identifiers so results are not assigned to the wrong order. Timeouts do not establish nonexecution; writes need idempotency or reconciliation. Completion claims must correspond to actual system evidence.
This uses a read-only lookup example without real order access. A fixed-response mock can check argument and result plumbing before authorized integration. Execution logs and target state remain independently necessary regardless of tidy JSON or a prose summary.
Checked sources
These sources support the concepts and methods described here. Examples and test scope are labeled separately; check the version of the tools you use.