gpt-5-nano
GPT-5 Nano is the smallest and fastest variant of the GPT-5 system, optimized for developer tools, rapid interactions and ultra-low-latency environments.
Pricing: Input 10 credits / 1M tokens (≈ $0.05), Output 80 credits / 1M tokens (≈ $0.40).
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GPT-5 Nano API on ModelFold
GPT-5 Nano is the smallest and fastest variant of the GPT-5 system, optimized for developer tools, rapid interactions and ultra-low-latency environments. Try GPT-5 Nano in the ModelFold Playground, then call it from your own code through an OpenAI-compatible chat completions API.
What Is the GPT-5 Nano API
GPT-5 Nano at a glance
GPT-5 Nano is a chat model from OpenAI. It accepts text, images and files (such as PDF) as input and returns text, with a context window of up to 400K tokens.
Use it without hosting anything
On ModelFold you call GPT-5 Nano with a single API key — no model weights to download and no inference servers to run. The same key also works for the other chat, image, video and audio models on ModelFold.
Core Capabilities of GPT-5 Nano
Up to 400K tokens of context
Keep long conversations, large documents and sizeable code in a single request, so the model can reason over the full material instead of fragments.
Understands images and files (such as PDF)
Besides text, GPT-5 Nano accepts images and files (such as PDF) as input, so a single request can combine instructions with visual or other media.
Function calling
GPT-5 Nano supports tool (function) calling: describe your functions in the request and the model returns structured calls your code can run — the basis for agents and integrations.
Adjustable reasoning effort
Choose a reasoning effort level (low, medium or high) per request to balance depth of thinking against speed and token usage.
Structured outputs
Ask for JSON that follows a schema (response_format), which makes extraction, classification and system integrations more reliable.
How to Use GPT-5 Nano on ModelFold
- 1
Step 1: Try it in the Playground
Open the Playground at the top of this page, type a prompt and see how GPT-5 Nano responds before writing any code.
- 2
Step 2: Create an API key
Sign in to ModelFold and create an API key in the console. Keep it secret and send it as a Bearer token.
- 3
Step 3: Send a request
Call POST https://modelfold.ai/v1/chat/completions with "model": "gpt-5-nano" and your messages. Existing OpenAI-compatible SDKs work by changing the base URL and key.
- ✓
Step 4: Ship and monitor
Integrate the response into your product and check token usage and spend for every call in the console logs.
What You Can Build with GPT-5 Nano
Low-latency experiences
Power chat interfaces, autocomplete and interactive tools where users expect fast responses.
High-volume pipelines
Run classification, extraction, rewriting and batch jobs at scale where cost per request matters.
Tool-calling backends
Route requests, call functions and chain API calls as the worker model inside larger agent systems.
AI coding assistants
Generate, explain, debug and refactor code, review pull requests and work through multi-file changes in developer tools and IDE plugins.
Frequently Asked Questions
What is GPT-5 Nano?⌄
GPT-5 Nano is the smallest and fastest variant of the GPT-5 system, optimized for developer tools, rapid interactions and ultra-low-latency environments.
Which inputs does GPT-5 Nano support?⌄
GPT-5 Nano accepts text, images and files (such as PDF) and returns text. Through ModelFold you can send text and images (OpenAI-style image_url content); in the Playground you can also attach documents, which are converted to text.
How long is the context window of GPT-5 Nano?⌄
Up to 400K tokens, shared between your input and the model’s output.
Does GPT-5 Nano support function calling?⌄
Yes. GPT-5 Nano supports tools / function calling through the standard tools parameter of the chat completions API.
How is GPT-5 Nano billed on ModelFold?⌄
Pay as you go by tokens: input and output tokens are charged at the per-million-token prices shown on this page. There is no monthly fee, and failed requests are not charged.
How do I call GPT-5 Nano through the API?⌄
Send a POST request to https://modelfold.ai/v1/chat/completions with "model": "gpt-5-nano", using your ModelFold API key as the Bearer token.
| Input | 10 credits 1M tokens≈ $0.05 |
| Output | 80 credits 1M tokens≈ $0.40 |
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 →AI Agents · Claude Code / Cursor / Trae →curl https://modelfold.ai/v1/chat/completions \
-H "Authorization: Bearer $MODELFOLD_API_KEY" \
-H "Content-Type: application/json" \
-d '{"model":"gpt-5-nano","messages":[{"role":"user","content":"Hello"}]}'