Now the spending, starting with the purchase you make before you type anything.
Instruction budget
Also called Short AGENTS.md
The limit you set on instructions that always load. AGENTS.md goes into every request, so each line has to earn its place on every task, including the many it has nothing to do with. Short and specific beats long and thorough.
Caching makes the dollars small, so that is not the main cost. Agents tend to do what these files say, so each needless requirement makes them do needless work, and a long file buries the rules that matter. Keep what the agent can't work out from the code, and cut the rest.
Say it to your agent
“Go through AGENTS.md line by line. Delete anything you could learn by reading the code, and any overview of the repo. Keep commands and rules the code can't show. Move rules that only apply to src/db/ into .claude/rules/db.md with a paths field. Get it under 100 lines and show me the diff.”