API vs Subscription
Subscriptions are for using AI tools. APIs are for building AI features into products.
Subscription
Pay a fixed monthly fee to use AI tools directly.
- ChatGPT / Claude / Gemini apps
- Codex / Claude Code / Cursor
- GitHub Copilot
API
Pay per usage to build AI into your own products.
- OpenAI API
- Anthropic API
- Google Gemini API
- DeepSeek API
Which do you need?
| Use case | Subscription | API |
|---|---|---|
| Personal coding | Good | Sometimes |
| Building a chatbot | No | Yes |
| Internal automation | Sometimes | Yes |
| SaaS feature | No | Yes |
| Cost per user control | Limited | Yes |
If you are using ChatGPT, Codex, Claude Code, Cursor, or Copilot directly, you may not need API pricing.
If you are building AI features into your own product, API pricing matters.
App-builder examples
Use these as starting shapes before opening the calculator. The token and request volumes mirror the calculator examples guide, and should be edited for your own product.
| Product pattern | Subscription is enough when | API pricing matters when | Start with |
|---|---|---|---|
| Support chatbot | Works for drafting replies manually. | Matters when customer messages trigger your product flow. | 1k input / 500 output x 10k requests Chatbot guide |
| RAG answer feature | Works for testing prompts with pasted context. | Matters when retrieved context is assembled per request. | 4k input / 800 output x 5k requests RAG guide |
| Document summarizer | Works for occasional manual documents. | Matters for batches, reports, transcripts, or uploads. | 20k input / 1k output x 1k requests Summarization guide |
| Coding-agent workflow | Usually enough for personal coding tools. | Matters when your app runs agent turns for users. | 8k input / 4k output x 2k requests Coding-agent guide |
Turn the decision into a cost check
If the API side fits, estimate one workload in the calculator, then compare candidate models with the same assumptions.