ModelFoldgemini-3.1-pro
Gemini 3.1 Pro is Google's Gemini 3.1 Pro Preview model (gemini-3.1-pro-preview), built by Google for better thinking and more grounded answers.
Pricing: Input 125 credits / 1M tokens (≈ $0.63), Output 875 credits / 1M tokens (≈ $4.38).
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Gemini 3.1 Pro API: Specs, API Key and Pricing on ModelFold
Gemini 3.1 Pro is Google's Gemini 3.1 Pro Preview model (gemini-3.1-pro-preview), built by Google for better thinking and more grounded answers. It reads up to 1,048,576 input tokens of text, images, video, audio and PDF and replies in text. On ModelFold you call it with an OpenAI-compatible chat completions request and your ModelFold API key.
Gemini 3.1 Pro API Parameters on ModelFold
ModelFold serves the model as gemini-3.1-pro for chat requests in the OpenAI chat completions format.
| Parameter | Value |
|---|---|
| Model | gemini-3.1-pro (Google model code: gemini-3.1-pro-preview) |
| Endpoint | POST https://ai.modelfold.online/v1/chat/completions, OpenAI chat completions format |
| Input token limit | 1,048,576 tokens |
| Output token limit | 65,536 tokens |
| Inputs | Text messages (the model itself can also read images, video, audio and PDF) |
| Output | Text |
| Reasoning effort | low or high; default high (adjustable in the Playground) |
| Thinking | Thought summaries can be shown in the Playground |
| Tools | Google Search grounding (available in the Playground) |
| Streaming | Not streamed; the API returns one JSON response with usage and credits charged |
| Pricing | Shown in the pricing card above |
What Gemini 3.1 Pro Does Well
Google describes Gemini 3.1 Pro Preview as refining the Gemini 3 Pro series with better thinking, improved token efficiency and more grounded, factually consistent answers.
Long, Mixed-Media Inputs
Long documents and media files can be read together in one request.
Reasoning You Can Dial
Set reasoning effort to high for harder problems or low for faster replies, and turn on thought summaries in the Playground when you want to see how it worked.
Answers Grounded in Search
Turn on the Google Search tool when an answer needs current information instead of only what the model already knows.
Clear, Parseable Replies
Describe the format you need in the prompt — for example a JSON object with named fields — when your code needs something it can parse rather than free text.
Gemini 3.1 Pro vs GPT-6 Astra: What the Leaderboards Show
Searchers often compare Gemini 3.1 Pro with GPT-6 Astra. The two leaderboards disagree: LMArena's text leaderboard scores Gemini 3.1 Pro Preview 1487 and GPT-6 Astra 1475 (as of October 8, 2026), while the Artificial Analysis Intelligence Index gives Gemini 3.1 Pro Preview 30 and GPT-6 Astra 53 (as of October 2026). The two measure different things: LMArena ranks models by human preference votes, while the Artificial Analysis index aggregates benchmark results. Test both on your own prompts; both models are available on ModelFold.
| Gemini 3.1 Pro | GPT-6 Astra | |
|---|---|---|
| LMArena text score (Oct 8, 2026) | 1487 | 1475 |
| Artificial Analysis Intelligence Index (Oct 2026) | 30 | 53 |
| Available on ModelFold | Yes | Yes |
Typical Uses for Gemini 3.1 Pro on ModelFold
On ModelFold the model handles chat requests. These are the kinds of tasks that fit.
Long-Document Questions
Questions answered across long reports, contracts or research papers in a single request.
Long Report and Transcript Analysis
Summaries and answers drawn from long reports, meeting transcripts and document text pasted into the conversation.
Research With Current Information
Answers that need fresh facts, with Google Search grounding switched on in the Playground.
Code Help in Chat
Writing, explaining and reviewing code inside a chat conversation.
How to Use the Gemini 3.1 Pro API on ModelFold
- 1
Step 1. Get Your API Key
Sign up on ModelFold, open the API Key Management page and create a key. Every request sends it in the Authorization header.
- 2
Step 2. Test Your Prompt in the Playground
You can try this model in the playground on this page without writing code. Compare low and high reasoning effort on the same prompt.
- ✓
Step 3. Send a Request
Send a POST request to https://ai.modelfold.online/v1/chat/completions with model set to gemini-3.1-pro and your messages, authenticated with your API key.
Tips Before You Ship
Use It for Chat, Not Agents Yet
On ModelFold this model supports chat requests only and has not been adapted for agent use; connecting it to an agent may cause request errors or unexpected results.
Send Text Messages
The ModelFold API takes an OpenAI-style messages array with text content. Paste document text into the message when you want the model to work with it.
Try Search and Thinking in the Playground
Google Search grounding, thought summaries and reasoning effort can be switched on in the Playground on this page, so you can compare answers before integrating.
Why Use Gemini 3.1 Pro on ModelFold
Same Key Across the ModelFold Market
All models in the ModelFold market use the same authentication method: an Authorization: Bearer YOUR_API_KEY header with the key from your ModelFold API Key Management page.
Free Credits to Start
New ModelFold users receive 80 free credits for testing. Your account has one credit balance that every model draws from, and you can see it, together with every charge, in your wallet.
Nothing to Host or Install
ModelFold provides this model as an API with a playground; there is no app to download or install. There are no GPUs or model weights to manage.
Frequently Asked Questions About Gemini 3.1 Pro API on ModelFold
How much does the Gemini 3.1 Pro API cost?⌄
Pricing is shown in the pricing card above.
How do I get a Gemini 3.1 Pro API key?⌄
On ModelFold you do not need a Google API key: create a key on the ModelFold API Key Management page and send it in the Authorization header. If you want Google's own key for Google's API, Google issues it in Google AI Studio.
Is Gemini 3.1 Pro free?⌄
Not on ModelFold: each request uses credits, as shown in the pricing card above. New ModelFold users receive 80 free credits for testing.
Is Gemini 3.1 Pro better than GPT-6 Astra?⌄
LMArena's text leaderboard puts Gemini 3.1 Pro Preview higher, and the Artificial Analysis Intelligence Index puts GPT-6 Astra higher; the comparison table above has the scores.
What is Gemini 3.1 Pro?⌄
Gemini 3.1 Pro is Google's Gemini 3.1 Pro Preview model for reasoning over long, multimodal inputs. On ModelFold it is the chat model gemini-3.1-pro; its parameters and uses are covered above.
What is the Gemini 3.1 Pro context window?⌄
Google lists an input limit of 1,048,576 tokens and an output limit of 65,536 tokens. The parameter table above has the other limits.
Does Gemini 3.1 Pro support Google Search?⌄
Yes. Google Search grounding can be switched on for this model in the Playground on this page when the answer needs current information.
What files can Gemini 3.1 Pro read?⌄
The model can read text, images, video, audio and PDF. The ModelFold API currently accepts text messages; check the latest API documentation for supported input formats.
| Input | 125 credits 1M tokens≈ $0.63 |
| Output | 875 credits 1M tokens≈ $4.38 |
Billed per token: input and output are priced separately, and thinking tokens count as output. The Playground charges exactly the same way.
Read API docs →curl https://ai.modelfold.online/v1/chat/completions \
-H "Authorization: Bearer $MODELFOLD_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model":"gemini-3.1-pro","messages":[{"role":"user","content":"Hello"}]}'