api-development

A practical guide to building on GPT-6 Astra: what reasoning effort actually costs you, what strict-mode structured outputs guarantee and what they do not, how the agentic tool surface fits together, and how to keep the bill sane.

Input tokens, output tokens, cached tokens and cache writes — what each one costs on GPT-6 Astra, what actually counts toward your input bill, and three worked examples showing where the money really goes.

Cached input tokens bill at a tenth of the standard rate. Here is exactly what gets cached, the 1,024-token minimum, why writes cost 1.25x, and the prompt-ordering mistakes that silently destroy your hit rate.

Autocomplete suggests a line you read before accepting. An agent makes twenty changes and runs commands. The difference is where verification moves to — and that is now the real cost.

JWTs look like scrambled text but are just three base64url-encoded segments. Learn their structure, how to decode one safely, and why decoding is not the same as verifying.

Base64 turns binary data into plain ASCII text, at the cost of about 33% more size. Here is how the encoding works, a real example, and the situations where you genuinely need it.