$ capsul glossary
Glossary
The words that decide what a coding agent costs, defined in one sentence each and then explained.
- Token
- A token is the unit a language model reads and bills in: a common word, a word fragment, or a punctuation mark, roughly three to four characters of English on average.
- Context window
- The context window is the maximum number of tokens a model can consider at once, covering the instructions, the conversation, and everything sent alongside the question.
- Input tokens and output tokens
- Input tokens are everything sent to the model on a request; output tokens are what it writes back, and in agent work the input side dominates the bill by an order of magnitude or more.
- Token budget
- A token budget is a hard ceiling on how much context is allowed into a request, enforced before the request is sent rather than negotiated with the model.
- Prompt caching
- Prompt caching lets a provider reuse the processed form of a repeated prefix across requests, billing those tokens at a fraction of the fresh rate.
- Cache hit rate
- The cache hit rate is the share of input tokens on a request that were served from a prompt cache rather than processed fresh.
- Context rot
- Context rot is the degradation in a model's answers as its context grows, through dilution of the relevant material, contradictions between old and new content, and accumulated dead ends.
- Agentic loop
- An agentic loop is the cycle in which a model calls a tool, reads the result, and decides what to do next, repeating until it produces an answer.
- Tool call
- A tool call is a structured request from a model to run something outside itself, such as reading a file or executing a command, whose result is fed back into the context.
- Repository map
- A repository map is a compressed outline of a codebase, listing its files and the symbols they define, so a model can locate things without reading everything.
- Rate limit and usage limit
- A rate limit caps how much you may send in a window of time, measured on tokens processed rather than on the number of messages sent.
- CLI coding agent
- A CLI coding agent is a command-line program that lets a model read, run and edit things in a working directory, under whatever approval rules you set.