Tokens & Pricing
Reasoning tokens
Extra output tokens some models generate as internal "thinking" before they produce a final answer. You're billed for them, but you usually never see them — they're the model working through the problem.
Example
You ask a reasoning model a hard math question. It answers in 50 visible tokens — but consumed 3,000 reasoning tokens getting there. Your bill reflects 3,050 output tokens, not 50. This is why a "short" answer from a reasoning model can cost more than a long answer from a standard one.
Related terms
Output tokens (completion tokens)
The tokens the model generates back to you. Output tokens almost always cost more per token than input tokens — often 3–5× more — because generating text is the expensive part.
Token
The unit AI models read and write, and the unit you're billed in. A token is a chunk of text — often a word, a piece of a word, or a punctuation mark. Models don't see letters or words; they see tokens.
Model tier
The rough class of a model by capability and price. Providers offer a range — small/fast/cheap up to large/slow/expensive — and the price gap between tiers is often 10–30×.