Overview
GPT-5 brings state-of-the-art language understanding, generation, and tool use, including the Codex coding variant. Native function calling and JSON mode make it a strong fit for structured, tool-driven applications.
What GPT-5 is best for
- Function calling and tool use
- Structured JSON output
- General-purpose chat and assistants
- Coding with the Codex variant
Strengths and tradeoffs
Strengths: Strong all-rounder, native function calling, JSON mode, competitive input pricing.
Tradeoff: 128K context is smaller than Claude's 200K. For very long documents, Claude has more room.
Pricing
| Metric | Price |
|---|---|
| Input tokens | $0.50 / 1M |
| Output tokens | $2.00 / 1M |
| Context window | 128K |
Estimate your own usage with the API cost calculator or count tokens with the token counter.
Quick start (Python)
GPT-5 runs through KissAPI's OpenAI-compatible endpoint, so any OpenAI SDK works. Just change the base URL and model id:
from openai import OpenAI
client = OpenAI(
api_key="YOUR_KISSAPI_KEY",
base_url="https://api.kissapi.ai/v1",
)
resp = client.chat.completions.create(
model="gpt-5",
messages=[{"role": "user", "content": "Explain async/await in one paragraph."}],
)
print(resp.choices[0].message.content)Works with Cursor, Claude Code, Cline, Aider, and any OpenAI-compatible client.
Use GPT-5 today
One API key for GPT-5 and 50+ other models. Pay per token, $1 free to start.
Start FreeFrequently asked questions
How much does the GPT-5 API cost?
Through KissAPI, GPT-5 is $0.50 per million input tokens and $2.00 per million output tokens, with a 128K context window.
What is GPT-5 best for?
Function calling and tool use, structured json output, and similar work.
How do I access GPT-5 without a OpenAI account?
Use KissAPI's OpenAI-compatible endpoint. Set your base URL to https://api.kissapi.ai/v1 and use model id gpt-5. No separate OpenAI account or VPN needed.