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Tool call · 5 checks · max 400 tokens · benched 2026-09-16

Gemini 3.1 Pro Preview vs Gemini 3.8 Flash vs Gemini 3.5 Flash Lite on pick the right tool of three

Google models side by side on "Pick the right tool of three": Gemini 3.5 Flash Lite scores 10/10; Gemini 3.5 Flash Lite is the cheapest answer scoring 8+ at $0.11 per 1,000 runs. Outputs, checks, judge reasons, latency and cost.

The prompt every model received

System

You are a function-calling engine. Reply with JSON only, no prose, no code fences.

User

You have three tools:
1. {"name": "search_docs", "parameters": {"query": "string"}}
2. {"name": "create_ticket", "parameters": {"subject": "string", "body": "string"}}
3. {"name": "get_order_status", "parameters": {"order_id": "string"}}

Choose exactly one tool for the user message and produce the call as a JSON object of the shape {"name": string, "arguments": object}.

User: Where is my order A1029? It was supposed to arrive yesterday.

Rubric for the judge: Selects get_order_status with order_id A1029 and nothing else; does not open a ticket or search docs.

Side by side

Every cell is one OpenRouter call at temperature 0 with the prompt's token cap and reasoning effort "low" where the model supports it. Cost is usage × the catalogue rate in models.json. Quality is one judge call to anthropic/claude-haiku-4.5 against the prompt's rubric, cached per prompt version.

Gemini 3.1 Pro Preview

google/gemini-3.1-pro-preview

10/10
Latency
2.0s
Cost
$0.00113
Per 1,000
$1.13

145 in · 70 out (45 reasoning) · 5 words · checks 5/5

  • json_valid
  • json_keys
  • regex
  • regex
  • not_contains
{"name": "get_order_status", "arguments": {"order_id": "A1029"}}

Judge: Output correctly selects get_order_status with order_id A1029 in proper JSON format, matching the rubric requirements exactly.

Gemini 3.8 Flash

google/gemini-3.8-flash

10/10
Latency
1.3s
Cost
$0.00020
Per 1,000
$0.20

145 in · 25 out · 5 words · checks 5/5

  • json_valid
  • json_keys
  • regex
  • regex
  • not_contains
{"name": "get_order_status", "arguments": {"order_id": "A1029"}}

Judge: Output correctly selects get_order_status with order_id A1029 in proper JSON format, matching the rubric requirements exactly.

Gemini 3.5 Flash Lite

google/gemini-3.5-flash-lite

10/10
top judge scorecheapest scoring 8+
Latency
466ms
Cost
$0.00011
Per 1,000
$0.11

145 in · 25 out · 5 words · checks 5/5

  • json_valid
  • json_keys
  • regex
  • regex
  • not_contains
{"name": "get_order_status", "arguments": {"order_id": "A1029"}}

Judge: Output correctly selects get_order_status with order_id A1029 in proper JSON format, matching the rubric requirements exactly.

Frequently asked

What does this prompt test?

Tool call: Selects get_order_status with order_id A1029 and nothing else; does not open a ticket or search docs. The deterministic checks are json_valid, json_keys, regex, regex, not_contains.

Which model should I pick for this task?

If the judge's bar of 8/10 is good enough for you, Gemini 3.5 Flash Lite at $0.11 per 1,000 runs. If you need the top score, Gemini 3.5 Flash Lite at $0.11 per 1,000 runs.

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