Structured, typed tool calls instead of free text — the reliable contract between model and code.
Category · Agentics
Structured calls instead of free text.
Function calling is the format modern LLMs use to emit tool calls — structured, typed, validatable. That replaces fragile prompt parsing with a reliable contract format between model and code.
Anthropic, OpenAI, Google each ship their own variant. MCP standardises this across vendors.
Why this matters in production.
Without structured calls, you're essentially building a parser for unreliable sentences. With function calling, tool calls become checkable contracts — which is what makes testing, monitoring and error handling serious in the first place.
See also
