Core Concepts
Input Tokens
Definition
The tokens in the prompt or request sent to an AI model. Input tokens include the system prompt, conversation history, and the user's current message. AI APIs typically charge a separate (usually lower) rate for input tokens.
In Plain English
The words you send to the AI. When you type a question, those words get converted into tokens, and you're charged for each one. Input tokens are usually cheaper than output tokens — it costs less for the AI to read than to write.