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AI Playbook

OpenAI: The GPT Ecosystem

📖 4 min read openaigptplatformecosystem
Complete guide to OpenAI's platform — GPT models, Responses API, Codex, MCP, Realtime API, image/video generation, Agent Skills, and enterprise deployment.
Key Takeaways
  • OpenAI's ecosystem spans 15+ products: GPT-5.5/GPT-5.4 models, Responses API, Codex (agentic coding), Realtime API, GPT Image 2, Sora, Whisper, and ChatGPT platform
  • Three core model tiers: GPT-5.5 ($5/$30, 1M ctx), GPT-5.4 ($2.50/$15, 1M), GPT-5.4 mini ($0.75/$4.50, 400K)
  • Codex runs on 7 surfaces: Desktop, IDE, CLI, Web, Chrome extension, GitHub Action, and SDK — plus Slack/Linear/GitHub integrations
  • ChatGPT platform includes MCP Apps SDK, Commerce, and Ads — a full application ecosystem beyond chat

OpenAI’s platform is the most expansive AI ecosystem — spanning frontier models, agentic coding, realtime voice/video, image generation, and an application platform within ChatGPT itself.

How the Ecosystem Connects

flowchart LR
    A["GPT Models\nGPT-5.5 · GPT-5.4 · mini · nano"] --> B["Responses API\nStreaming · Caching · Batch · Tools"]
    B --> C["Developer Platform\nCodex · Agents SDK · MCP · Skills"]
    B --> D["ChatGPT Platform\nChat · MCP Apps · Commerce · Ads"]
    B --> E["Media & Realtime\nGPT Image 2 · Sora · Realtime · Whisper"]
    C --> D

Product Directory — At a Glance

ProductWhat It IsWho It’s ForHow to Access
GPT-5.5Flagship model for complex reasoning/codingAdvanced developers, R&Dplatform.openai.com
GPT-5.4 / 5.4 mini / 5.4 nanoAffordable tier across three sizesMost production workloadsplatform.openai.com
CodexAgentic coding platform across 7 surfacesDevelopers, engineering teamscodex.openai.com
ChatGPTWeb/mobile/desktop chat interfaceEveryonechatgpt.com
Responses APIPrimary API endpoint (replaces Chat Completions)Developersplatform.openai.com
Agents SDKBuild and orchestrate AI agentsDevelopers, platform teamsopenai Python/TS SDK
Realtime APIVoice agents, live translation, speechVoice/audio developersWebRTC, WebSocket, SIP
GPT Image 2State-of-the-art image generationDesigners, creators, appsAPI + ChatGPT
SoraCinematic video generationVideo creatorsChatGPT / API
Whisper / TTSSpeech-to-text and text-to-speechTranscription, voice appsAPI
MCP & ConnectorsConnect AI to external tools and dataDevelopers, platform buildersplatform.openai.com
ChatGPT Apps SDKBuild MCP apps that run inside ChatGPTApp developersdevelopers.openai.com
ChatGPT CommerceShopping and commerce flows in ChatGPTRetailers, merchantsopenai.com/commerce
ChatGPT EnterpriseBusiness plans, SSO, admin controlsOrganizationsopenai.com/enterprise
ChatGPT AdsAdvertise within ChatGPTAdvertisersopenai.com/ads

Model Tiers — Quick Compare

ModelAPI Price (in/out)ContextBest For
GPT-5.55/5 / 30 per 1M1M tokensComplex reasoning, agentic coding, professional work
GPT-5.42.50/2.50 / 15 per 1M1M tokensAffordable coding, most production workloads
GPT-5.4 mini0.75/0.75 / 4.50 per 1M400K tokensCoding, computer use, subagents
GPT-5.4 nano~0.15/ 0.15 / ~0.60 per 1M400K tokensFastest, cheapest, high-throughput

Note: Playbook previously listed GPT-5.5 at 2/2/8. The current official pricing is 5/5/30 per 1M tokens. GPT-5.5 has reasoning capabilities (none/low/medium/high/xhigh). See GPT Models for the full comparison.

Decision Tree: Which OpenAI Product?

What do you want to do?
│
├─ Build AI-powered applications → Responses API + SDKs
├─ Write code, refactor, debug → Codex (Desktop, IDE, or CLI)
├─ Chat, research, generate images → ChatGPT (chatgpt.com)
├─ Add voice/audio to your app → Realtime API (WebRTC/WebSocket)
├─ Generate images programmatically → GPT Image 2 API
├─ Build custom AI agents → Agents SDK
├─ Deploy an app inside ChatGPT → ChatGPT Apps SDK (MCP)
├─ Standardize team coding workflows → Agent Skills (SKILL.md)
├─ Sell products through ChatGPT → ChatGPT Commerce
├─ Enterprise SSO, admin, compliance → ChatGPT Enterprise
└─ Explore cutting-edge → See individual pages below

Where to Go Next