Build a Token Ledger Before You Burn Through a Free Model Tier

Disclosure: This article was prepared as part of MonkeyCode's product outreach. Why this is worth reading: a free model endpoint with a large token allowance is a good place to validate a new CLI workflow, but it can burn through the allowance in a single retry loop before you notice. I built a small stateful budget guard that checks the projected cost before the call, records actual usage after the call, and refuses to touch the ledger when the endpoint sends an unexpected response. It works as a disposable first pass on a free endpoint and leaves you a clean exit when the shape changes. MonkeyCode's outreach describes an open-source project with a free model route and a free hosted server. I do not treat either as a permanent dependency. I treat them as a test target: an endpoint I can call without a contract while I am still changing prompts, timeouts, and schemas. The tool below is independent of MonkeyCode's exact model list; it assumes only an OpenAI-style chat completion path and usage accounting in the response. Swap one function if the free server does not follow that shape. The problem with a free allowance Most model dashboards report aggregate usage after the fact. That is enough for casual work, but it is not enough when you wire an endpoint into a loop. I have seen two avoidable failures in my own drafts. A retry-on-timeout wrapper restarted a slow request four times before the first response arrived, multiplying total token spend. A long context buffer kept sending the same 6k-token history on every turn because I forgot to trim old messages. The dashboard showed the total drop, but not which call caused it. A local ledger fixes that by refusing to send the request when the projected total exceeds the budget. It does not replace the provider dashboard. It makes the decision before the endpoint gets a chance to consume tokens. The artifact The script below does three jobs: load a budget and already-used amount from a JSON file make a conservative prefl