gpt-oss-20b
gpt-oss-20b is an open-weight 21B-parameter model from OpenAI released under the Apache 2.0 license. It uses a Mixture-of-Experts architecture with 3.6B active parameters per forward pass.
Pricing: Input 6 credits / 1M tokens (≈ $0.03), Output 26 credits / 1M tokens (≈ $0.13).
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gpt-oss-20b API on ModelFold
gpt-oss-20b is an open-weight 21B-parameter model from OpenAI released under the Apache 2.0 license. It uses a Mixture-of-Experts architecture with 3.6B active parameters per forward pass. Try gpt-oss-20b in the ModelFold Playground, then call it from your own code through an OpenAI-compatible chat completions API.
What Is the gpt-oss-20b API
gpt-oss-20b at a glance
gpt-oss-20b is a chat model from OpenAI. It accepts text as input and returns text, with a context window of up to 131K tokens.
Use it without hosting anything
On ModelFold you call gpt-oss-20b 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-oss-20b
Up to 131K 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.
Function calling
gpt-oss-20b 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-oss-20b on ModelFold
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Step 1: Try it in the Playground
Open the Playground at the top of this page, type a prompt and see how gpt-oss-20b responds before writing any code.
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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-oss-20b" 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-oss-20b
High-volume pipelines
Run classification, extraction, rewriting and batch jobs at scale where cost per request matters.
Low-latency experiences
Power chat interfaces, autocomplete and interactive tools where users expect fast responses.
Analysis and complex reasoning
Work through research questions, data interpretation, planning and other problems that need careful step-by-step reasoning.
Tool-calling backends
Route requests, call functions and chain API calls as the worker model inside larger agent systems.
Frequently Asked Questions
What is gpt-oss-20b?⌄
gpt-oss-20b is an open-weight 21B-parameter model from OpenAI released under the Apache 2.0 license. It uses a Mixture-of-Experts architecture with 3.6B active parameters per forward pass.
Which inputs does gpt-oss-20b support?⌄
gpt-oss-20b accepts text and returns text. Through ModelFold you send text messages; documents attached in the Playground are converted to text.
How long is the context window of gpt-oss-20b?⌄
Up to 131K tokens, shared between your input and the model’s output.
Does gpt-oss-20b support function calling?⌄
Yes. gpt-oss-20b supports tools / function calling through the standard tools parameter of the chat completions API.
How is gpt-oss-20b 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-oss-20b through the API?⌄
Send a POST request to https://modelfold.ai/v1/chat/completions with "model": "gpt-oss-20b", using your ModelFold API key as the Bearer token.
| Input | 6 credits 1M tokens≈ $0.03 |
| Output | 26 credits 1M tokens≈ $0.13 |
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-oss-20b","messages":[{"role":"user","content":"Hello"}]}'