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OpenAI gives you three lines to choose between: the flagship GPT, the lighter and cheaper mini tier, and a separate o-series built for deep step-by-step reasoning. The choice usually comes down to a balance: how smart versus how fast and cheap. This page helps you pick a model for the task and understand what GPT can do. For the technical setup see the Quickstart; this page is about the models themselves.

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How the lines differ

LineStrong atSpeed / costWhen to use
Flagship GPTAll-rounder: code, analysis, vision, long contextMediumDaily work, code, multi-step tasks
miniSimple tasks at high volumeFaster, cheaperChatbots, classification, bulk processing
o-series (reasoning)Deep step-by-step reasoning, math, logicSlower, pricierHard problems that need a chain of thought
Not sure? Start with the flagship GPT — it covers most tasks. Move to mini when speed and cost matter more than peak quality, and to the o-series when the task needs real reasoning rather than a quick answer.

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What GPT can do

  • Vision — you can pass images as input: screenshots, diagrams, scans. See image input for the request format.
  • Function calling (tool use) — the model returns structured tool calls, which is what agents and integrations are built on. See function calling for a full example.
  • Long context — a large window that fits whole documents and chunks of a codebase.
  • Reasoning (o-series) — a separate line that “thinks” before answering, breaking the task into steps; it helps with math, logic and hard code.
  • Embeddings — turn text into vectors for semantic search and RAG; see embeddings.
For long answers, you can also stream the response token by token instead of waiting for the full reply.
In the model field you pass an ID, for example gpt-5 for the flagship model. Exact names, versions and per-token prices are on the Pricing page at www.ruapi.ai. Names match OpenAI’s official ones, and new versions appear in the catalog automatically.

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Picking by task

  • General tasks, chat, code → flagship GPT by default.
  • High request volume where speed and cost matter → mini (chatbots, classification, tags at scale).
  • Hard reasoning, math, logic → o-series.
  • Images as input → flagship GPT with vision.
  • An agent or a tool pipeline → flagship GPT (reliable tool use).

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How to connect

GPT is served over the OpenAI-compatible protocol, so any OpenAI SDK or a tool like Cursor, Cline or n8n works — just point base_url at https://www.ruapi.ai/v1. Step by step in the Quickstart.

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FAQ

The flagship is the everyday choice: code, analysis, vision. Reach for mini when you have lots of requests and speed plus cost matter — chatbots, classification, short answers at scale.
It’s a separate line of models that “thinks” through the task step by step before answering. It’s strong at math, logic and hard code, but slower and pricier than regular GPT — use it selectively, for genuinely tough problems.
Yes, models with vision accept images as input alongside text — screenshots, diagrams, scans.
Large — it fits whole documents and chunks of code. The exact limit depends on the version and matches OpenAI’s official one.
You create a key in your dashboard on the main site, then drop it into any OpenAI-compatible tool. Step by step in the Quickstart.
You top up your balance in USDT — no cards or VPN needed. The how-to is on the Top up page.

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Next

Connect and first request

base_url, key, Python and curl code.

Claude models

Same key — choosing and using Claude.