gpt-5-5GPT-5.5 is OpenAI’s advanced reasoning model for agentic coding, knowledge work, scientific research, and complex multi-step task execution. Served via the Responses API (`/v1/responses`) with adjustable reasoning effort (low–xhigh), web search, function calling, and multimodal input. Drop-in for OpenAI Codex CLI with wire_api = "responses".
Frontier reasoning for agentic coding, research, and complex multi-step work
reasoning.effort = low / medium / high / xhigh
Built-in web search or function calling (one per request)
Cached input billed at $0.1 / 1M; reasoning tokens count as output
View complete API reference with all parameters and examples.
Enable real-time streaming responses with Server-Sent Events.
{
"model": "gpt-5-5",
"stream": true,
"messages": [...]
}Enable the model to use tools and call functions.
{
"model": "gpt-5-5",
"tools": [{
"type": "function",
"function": {
"name": "get_weather",
"description": "Get current weather for a location",
"parameters": {
"type": "object",
"properties": {
"location": {"type": "string", "description": "City name"}
},
"required": ["location"]
}
}
}],
"messages": [{"role": "user", "content": "What's the weather in Tokyo?"}]
}Get structured JSON responses from the model.
{
"model": "gpt-5-5",
"response_format": {"type": "json_object"},
"messages": [{"role": "user", "content": "Extract info as JSON: John is 30 years old"}]
}| Parameter | Type | Required | Description |
|---|---|---|---|
| model | string | Yes | Model identifier (e.g., gpt-5-5) |
| messages | array | Yes | Array of message objects with role and content |
| max_tokens | integer | No | Maximum tokens in the response |
| stream | boolean | No | Enable streaming responses (SSE) |
| temperature | number | No | Sampling temperature (0.0 - 2.0) |
| top_p | number | No | Nucleus sampling threshold (0.0 - 1.0) |
| tools | array | No | Function calling tools definition |
| response_format | object | No | Output format (e.g., json_object) |
View complete API reference with streaming, thinking, and more.
Billing: Cost = (input_tokens * input_price + output_tokens * output_price) / 1,000,000
GPT-5.5 is a Large Language Model API provided by OpenAI. GPT-5.5 is OpenAI’s advanced reasoning model for agentic coding, knowledge work, scientific research, and complex multi-step task execution. Served via the Responses API (`/v1/responses`) with adjustable reasoning effort (low–xhigh), web search, function calling, and multimodal input. Drop-in for OpenAI Codex CLI with wire_api = "responses". Through API Models platform, you can access this model via a unified API at prices significantly lower than official rates. Current pricing: Input: $3, Output: $18 per 1M tokens.
Build intelligent conversational systems to automatically answer user queries and improve service efficiency.
Automatically write articles, emails, ad copy, and other text content to boost productivity.
Assist with code writing, debugging, and code review to accelerate software development.
Understand and analyze unstructured data, extract key insights, and generate summary reports.
GPT-5.5 is available through API Models at: Input: $3, Output: $18 per 1M tokens. This is up to 95% cheaper than official pricing.
Sign up at API Models, get your API key, and call our unified API endpoint. We provide detailed API documentation with code examples in cURL, Python, and Node.js.
API Models offers the same GPT-5.5 model at 60-95% lower cost through our aggregation platform. We provide a unified API interface so you do not need separate accounts for each provider - one API key to access all models.
GPT-5.5 is a frontier reasoning model served on the OpenAI Responses API with tunable reasoning effort (low→xhigh). It excels at hard, multi-step problems and agentic coding — it is the model behind OpenAI Codex CLI when pointed at API Models (wire_api = responses). Higher effort spends more reasoning tokens, billed as output.
GPT-5.5 is the newer, stronger tier for the hardest tasks; GPT-5.4 is cheaper and fast enough for most coding and agent work. Both run on the Responses API and work in Codex CLI — switch by changing one model name.
Yes — function calling and the built-in web_search tool both work (mutually exclusive per request). Tool calls drive Codex CLI's local file and shell operations. See /docs/codex.
On API Models, GPT-5.5 runs alongside 60+ models on one API key and one balance, so choosing is about fit, not lock-in. It supports Agentic Coding, Deep Reasoning, Web Search, Multimodal, and you can weigh it on price and capability against other Large Language Model models, then switch by changing a single model-name string — no new account or integration. Browse every Large Language Model option with live pricing at apimodels.app/models.
GPT-5.5 supports: Agentic Coding, Deep Reasoning, Web Search, Multimodal. See the API Models docs for full parameters and call examples.
Yes. API Models exposes GPT-5.5 through a single unified API and one key — no separate provider accounts, and no need to handle each provider's regional network access yourself.
We support Stripe (Visa, Mastercard, and other international cards) and Alipay. Credits are available instantly after payment.