Function calling in 2026 — patterns that actually work

Function calling used to be a fragile prompt trick. In 2026 it's a first-class protocol supported natively by every frontier model on TokenBaazar.

The canonical loop#

while True:
    r = client.chat.completions.create(model=model, messages=msgs, tools=TOOLS)
    msg = r.choices[0].message
    msgs.append(msg)
    if not msg.tool_calls:
        break
    for tc in msg.tool_calls:
        result = dispatch(tc.function.name, tc.function.arguments)
        msgs.append({"role": "tool", "tool_call_id": tc.id, "content": result})

Parallel tool calls#

Modern models return multiple tool_calls in one turn. Execute them concurrently — a naïve serial loop wastes 3-5× wall time.

Guardrails#

• Cap loop iterations (default 8)
• Log every dispatch with args + latency
• Reject unknown tool names hard — don't hallucinate a handler
• Truncate massive tool outputs before appending