GPT-5.5 API: OpenAI's frontier model, one key away
GPT-5.5 via the ApexApi gateway
GPT-5.5 is OpenAI's flagship multimodal model — strong general reasoning, long-context understanding, reliable tool/function calling, and high-quality code generation. Through ApexApi you call it with one OpenAI-compatible key, alongside every other major model.
GPT-5.5 is served through ApexApi's unified, OpenAI-compatible API — one key, one format, with smart routing and automatic failover. Provider: OpenAI.
Why GPT-5.5
Frontier reasoning
Handles multi-step logic, analysis, and complex instructions with high fidelity.
Tool & function calling
Robust structured outputs and tool orchestration for agentic and automation workloads.
Multimodal + long context
Processes long inputs and mixed content for document analysis, RAG, and assistants.
Specifications
- Modality
- chat
- Context window
- 1050K tokens
- Max output
- 128K tokens
- Streaming
- Yes
- Tool / function calling
- Yes
- Vision input
- Yes
GPT-5.5 pricing
Pay-per-use — no subscription, no minimums. Buy credits and pay only for what you call. Transparent, per-call pricing across every model.
Getting started with GPT-5.5
OpenAI-compatible — point your client at ApexApi, swap your key, and call it. No new SDK to learn.
from openai import OpenAI
client = OpenAI(
base_url="https://api.apexapi.dev/v1",
api_key="<YOUR_APEXAPI_KEY>",
)
response = client.chat.completions.create(
model="openai/gpt-5.5",
messages=[{"role": "user", "content": "Hello!"}],
)
print(response.choices[0].message.content)GPT-5.5 use cases
What teams build with GPT-5.5 on ApexApi.
Coding assistants
Code generation, refactoring, reviews, and multi-file reasoning.
Agents & automation
Tool-using agents that call APIs and orchestrate multi-step workflows.
Knowledge assistants
RAG, summarization, and long-document Q&A with citations.
GPT-5.5 vs other models
How it compares — and on ApexApi you can switch between any of them with a single string change, same key, same endpoint.
GPT-5.5 vs Claude Opus 4.7
Opus 4.7 leans into careful long-form analysis and agentic coding; GPT-5.5 emphasizes broad multimodal reasoning and tool orchestration. On ApexApi you can A/B them with one key.
Learn more about Claude Opus 4.7 API →GPT-5.5 vs Gemini 3.1 Pro Preview
Gemini 3.1 Pro is built around deep native multimodality and very long context; GPT-5.5 centers on instruction fidelity and tool use.
Learn more about Gemini 3.1 Pro Preview API →GPT-5.5 vs DeepSeek V4 Pro
DeepSeek V4 Pro is a cost-efficient powerhouse for coding and reasoning; GPT-5.5 is the broad frontier generalist.
Learn more about DeepSeek V4 Pro API →Why build on ApexApi
One API, every model
OpenAI-compatible — swap the base URL and key, keep your code. Call 14+ providers and hundreds of models through a single integration.
Smart routing & failover
Per-model provider chains with automatic failover. If one provider degrades, requests route to the next — your app stays up.
Pay-per-use, no lock-in
Buy credits, pay only for what you call. No subscriptions, no minimums. Switch models anytime with a single string change.
GPT-5.5 API — FAQ
How do I use the GPT-5.5 API?
Create an ApexApi key, then point your client at https://api.apexapi.dev/v1 and use the model slug. Send a request to /v1/chat/completions with the model slug — the API is OpenAI-compatible, so most OpenAI SDKs work by changing the base URL and key.
Is the GPT-5.5 API OpenAI-compatible?
Yes. ApexApi exposes GPT-5.5 through the same OpenAI-compatible interface used across the whole catalog — swap the base URL and API key and keep your existing code.
How much does GPT-5.5 cost on ApexApi?
Pay-per-use — see the live price in the Pricing section above. There's no subscription or minimum; you buy credits and pay only for what you call.
Can I switch from GPT-5.5 to another model later?
Yes — change a single string (the model slug) to call any other model in the catalog through the same endpoint and key. No re-integration.
Ready to build with GPT-5.5?
One API key. Every major AI model. Pay only for what you use.
Get your API key — free to start