Start with a task contract

For difficult work, specify the goal, constraints, available tools, acceptance criteria and expected output format. This is more robust than adding vague instructions such as “think harder.”

Separate requirements from context

Long context does not eliminate prompt design. Put authoritative requirements where they are easy to identify, distinguish source material from instructions, and avoid dumping irrelevant documents into the context simply because the window is large.

Make tool boundaries explicit

For agentic tasks, define what the model may change, what requires confirmation, what systems it can access and how completion should be verified.

Evaluate prompts like code

Version important prompts, keep a representative test set and compare quality, latency and token cost whenever you change instructions or reasoning effort.

Primary sources

Specifications and prices can change. We prefer first-party documentation and record the date each page was reviewed.

  1. OpenAI Developers — GPT-6 Astra model page
  2. OpenAI — GPT-6 Astra announcement