Build a Token budget from real requests

Agree on the billing basis

Start with the current model and its billing rules. Check currency, units, and whether input, output, and cached usage have separate rates. Public pricing explanations describe the structure; verify the actual available configuration and current rates through official information and your account.

A chat subscription and developer API access serve different workflows. An existing chat subscription does not establish API credits for an application. Compare allowance periods and restrictions alongside expected usage rather than comparing monthly headline amounts alone.

Measure the pieces of a request

Run representative tasks and record the input contributed by system instructions, conversation history, retrieved passages, and tool results. Measure actual output too. An agent can carry context repeatedly and make several calls for one user action, so the short user prompt is a poor spending estimate.

Estimate a range and reconcile

For matching units, estimate each billable category as quantity multiplied by its rate, then add the categories. Separate cached input only when confirmed rules and observed hits justify it; avoid counting it twice. Multiply task-level calls by expected business volume and allow room for longer outputs, context growth, and recovery.

Set budget limits and alerts, run a small pilot, and compare estimates with usage records. Investigate model selection, units, caching, and repeated calls when the numbers differ. Save your assumptions and calculation date, then measure again after changing a model or prompt.