Gemini 3.1 Pro Preview Custom Tools API Pricing
Google · context window 1M · prices updated 2026-09-15
Where Gemini 3.1 Pro Preview Custom Tools sits on price
At $12.00 per million output tokens, Gemini 3.1 Pro Preview Custom Tools is a premium tier model — 5.8× the median output price of $2.08, which puts it cheaper than 18% and pricier than 82% of the models we track. It sits 36th cheapest of the 38 Google models we track. Output costs 6.0× more than input here, so anything that makes the model write less — tighter instructions, structured output, lower max_tokens — moves the bill more than trimming the prompt.
Cached input is 90% cheaper. On an input-heavy workload you need roughly a 28% cache-hit rate to take 25% off the input line — reachable for chatbots and agents that resend the same system prompt and history.
What real workloads cost on Gemini 3.1 Pro Preview Custom Tools
These three workloads are the ones teams actually run on a premium-priced model — a $12.00/1M model is not bought for the same job as one ten times the price.
| Workload | Per request | Per month |
|---|---|---|
| Support chatbot — 500 conversations/day (5K in / 1.4K out) Conversation history re-sent each turn — the classic prompt-caching win. | $0.0268 | $402 |
| Coding agent — 300 sessions/day (60K in / 12K out) Multi-step loops re-read the same files; caching matters more than raw price. | $0.264 | $2376 |
| Long-context analysis — 200 runs/day (250K in / 4K out) Only possible on large-context models; input cost is nearly the whole bill. | $0.548 | $3288 |
Model your exact traffic in the API cost calculator — it preloads Gemini 3.1 Pro Preview Custom Tools with caching and batch options.
Gemini 3.1 Pro Preview Custom Tools price history
Gemini 3.1 Pro Preview Custom Tools's price has not moved since we began tracking it on Aug 2, 2026 — 44 days of stability in a market where 78 of the 334 models we track have repriced over the same period, including 6 of Google's own 38 models.
Change-points from our daily price snapshots (tracking since Aug 2, 2026; intraday moves between snapshots are not captured).
Gemini 3.1 Pro Preview Custom Tools vs GPT-5.6 Terra Pro
The closest-priced alternative from another vendor is GPT-5.6 Terra Pro (OpenAI) — priced within a rounding error on output, with identical input pricing. When two models land this close on price, the decision is quality on your own workload, not the price sheet: run 50 real requests through both and compare.
See GPT-5.6 Terra Pro pricing →Cheaper alternatives
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Frequently asked questions
› How much does the Gemini 3.1 Pro Preview Custom Tools API cost?
Gemini 3.1 Pro Preview Custom Tools costs $2.00 per million input tokens and $12.00 per million output tokens, with cached input at $0.2 per million (90% cheaper). That works out to roughly 83,333 output tokens per dollar.
› What does the support chatbot workload cost on Gemini 3.1 Pro Preview Custom Tools?
Support chatbot — 500 conversations/day (5K in / 1.4K out) costs about $0.0268 per request and $402 per month on Gemini 3.1 Pro Preview Custom Tools. Conversation history re-sent each turn — the classic prompt-caching win.
› What does it cost to fill Gemini 3.1 Pro Preview Custom Tools's 1M context window?
Sending 1M of input in a single request costs $2.10 at $2.00 per million tokens — before any output. With prompt caching that same fill drops to about $0.2097 on repeat requests. This is why large context windows are cheap to advertise and expensive to actually use.
› Is Gemini 3.1 Pro Preview Custom Tools worth the price?
Gemini 3.1 Pro Preview Custom Tools sits in the middle of the market (36 of 38 by price within Google). The honest test is a routing experiment: send the same 200 real requests to this model and to a tier below, and compare failure rate against the price gap — most teams find a majority of traffic never needed the pricier model.