Where do I create an API key and buy tokens?

Both happen on api.reapi.ai — the chat workspace runs as its own platform separate from the image / video task gateway at reapi.ai. Sign up at api.reapi.ai, generate a key under API Keys, and top up under Top Up. A reapi.ai/settings/apikeys key will not authenticate against the chat endpoint.

Is the GPT-5.5 API OpenAI-compatible?

Yes. The GPT-5.5 API is a drop-in for OpenAI's /v1/chat/completions — same request shape, same `messages` array, same `stream` / `temperature` / `top_p` / `frequency_penalty` / `presence_penalty` parameters, same SSE wire format. Most teams migrate by changing the base URL to https://api.reapi.ai/v1, swapping the API key, and setting `model: "gpt-5.5"`.

What is the GPT-5.5 context window?

GPT-5.5 has a 1M token context window and supports up to 128K output tokens per response. For sessions where the prompt exceeds 272K tokens, long-context pricing applies at 2× input and 1.5× output rates — see the pricing card on this page for the resolved per-1M-token numbers.

How is GPT-5.5 different from GPT-5.4?

GPT-5.5 is positioned as the newer GPT option for demanding reasoning workflows: 1M context, 128K max output, and improved tool-using behaviour with Tool Search. GPT-5.4 remains useful when you want a lower-cost route for established production traffic that doesn't need the new reasoning capabilities — both share the same endpoint and OpenAI-compatible wire format.

What is the >272K long-context billing rule?

When the input portion of a single request exceeds 272K tokens, the entire request is billed at 2× input and 1.5× output. Requests at or below 272K input use the standard rate — see the pricing card on this page for the resolved per-1M-token numbers in both tiers.

What is the `group` parameter?

`group` selects a token group on the api.reapi.ai gateway, which routes the request to a specific channel pool. `default` is the standard pool and covers nearly every workload. You can leave the field out of the body if you're happy with the default routing.

GPT-5.5 API — Frontier Reasoning, OpenAI-Compatible

GPT-5.5 is OpenAI's newest reasoning model — a drop-in OpenAI-compatible /v1/chat/completions endpoint with 1M context, 128K max output, advanced reasoning with adjustable effort, and Tool Search for large agent workflows. Pay-as-you-go pricing in USD.

GPT-5.5modelgpt-5.5

GPT-5.5 playground

Open the chat playground to run GPT-5.5 through the OpenAI-compatible chat completions surface with your api.reapi.ai key.

Open chat playground

What you can build with this model

Real-world workflows and production use cases you can build and ship with this model.

GPT-5.5 reasoning over a multi-step task

Run complex multi-step reasoning workflows

Build research agents, decision-support systems, and long-running planners on the GPT-5.5 API. Advanced reasoning with adjustable effort (`none` to `xhigh`) lets you trade latency for depth on a per-call basis — production teams can dial reasoning down for cheap turns and up for the hard ones.

Read the API docs

GPT-5.5 analysing a full repository in one request

Full-codebase analysis with 1M context

Process entire repositories, long technical documents, or large research sets in a single request. The GPT-5.5 API's 1M token context window makes whole-codebase refactoring, audit, and generation practical from a single /v1/chat/completions call.

GPT-5.5 selecting tools dynamically from a large registry

Enterprise tool orchestration with Tool Search

Wire GPT-5.5 into workflows that need many tools, internal APIs, or MCP connectors. Tool Search lets the model pull only the tools it needs on demand instead of dumping every definition into every prompt — agent quality improves and token waste drops.

Pricing

Credit-based — 1 credit = $0.001 USD. Pay only for completed generations.

Category	Unit	Price
Tokens
Input tokens	1M tokens	$2
Output tokens	1M tokens	$12

Why reAPI

OpenAI-compatible migration path

The GPT-5.5 API speaks OpenAI Chat Completions verbatim. For most teams, moving an existing OpenAI integration is a base URL, an API key, and a model-string change — not a platform rewrite. The same `messages` array, the same `stream`, `temperature`, `top_p`, `frequency_penalty`, and `presence_penalty` parameters, the same SSE wire format.

Pay-as-you-go pricing in USD

GPT-5.5 is billed pay-as-you-go in USD — current per-1M-token rates are listed in the pricing card on this page so you can estimate production cost before routing real workloads. Top up once, your balance is drawn down per request, no monthly minimum.

One key across GPT, Claude, and Gemini

A single api.reapi.ai key unlocks GPT-5.5 alongside Claude Opus 4.7, Gemini 3.1 Pro, and every other frontier chat model on the platform. That makes vendor comparison, fallback routing, and per-call cost optimisation a configuration change instead of an integration project.

Ship the GPT-5.5 API in three steps

step 01
Create an account and key on api.reapi.ai
Sign up at api.reapi.ai, open the console, generate an API key under API Keys, and top up tokens under Top Up. The chat workspace is separate from the reapi.ai image/video gateway — keys do not cross over.
Open
step 02
Send your first request
POST https://api.reapi.ai/v1/chat/completions with `model: "gpt-5.5"`, your `messages` array, and any optional parameters. The endpoint is OpenAI-compatible, including streamed responses.
Open
step 03
Read the API docs
Open the GPT-5.5 docs for the full request schema, the >272K long-context billing rule, error envelope, and language-specific code samples (cURL, Python, Node.js, Go).
Open

Frequently asked questions

Common questions about this model.

GPT-5.5 is billed pay-as-you-go in USD against your api.reapi.ai token balance — see the pricing card on this page for the live per-1M-token rate. The bill is `(prompt_tokens × input_rate + completion_tokens × output_rate) / 1,000,000`. Top up at api.reapi.ai; failed requests are not charged.

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What you can build with this model

Real-world workflows and production use cases you can build and ship with this model.