OpenAI

An email popped up in my inbox today: “You can just build things, enjoy 6 months on us.” Sender: the Codex team at OpenAI. The first line, in big letters: “You’re in.” Then: “Thanks for maintaining open source projects.” I stared at that line three times and couldn’t help laughing out loud. Free ride: secured A while back I filled out their Codex for Open Source application on a whim. Didn’t expect much — I just listed the PRs I’d submitted to context-mode, plus my own byf and dev-skills.

We often see URLs like these: 1 2 3 /v1/chat/completions /v1/messages /v1/responses These suffixes are not decoration — they define a complete request and response data structure. Pick the wrong one and your code either errors out or silently loses data. This article starts at /v1/completions and works its way to /v1/responses, explaining what each suffix stands for, why it was designed that way, and where the common pitfalls are.