Prompt Optimizer

Optimize prompts for Claude's latest models — the Claude 5 family (Opus 5, Sonnet 5, Fable 5) plus the still-active Opus 4.8, Sonnet 4.6, and Haiku 4.5 — using Anthropic's official guidance. Diagnose what is wrong, pick the right lever, apply a proven fix, then measure.

Two levers, not one

Many problems people try to fix by editing prompt wording are better fixed with an API parameter. Always weigh both:

1. Prompt — wording, structure, examples, role, explicit scope.
2. Parameters — effort (intelligence vs. speed/cost), thinking (adaptive on/off), max_tokens (room to think and act).

On the latest models, effort is frequently the highest-leverage change. If reasoning is shallow on a hard task, raise effort to high/xhigh instead of prompting around it. If the model overthinks or over-explores, lower it. Detail in references/model-tuning.md.

What changed for the latest models

These shifts change how to optimize. Do not carry over old habits blindly: