Member-only story
Anthropic Just Revealed 12 New Rules for Prompting Claude Opus 5.5
Developers Need to Rethink Their Prompts
Not a Member? Read for FREE here.
If you have been writing prompts for Claude the same way you did six months ago, there is a good chance you are now giving the model instructions it doesn’t need.
Worse, some of those instructions can make your AI agent slower, more expensive, or even stop before the job is finished.
Anthropic’s new Claude Opus 5.5 changes the prompting game in a subtle way.
The model is designed for long-running agentic coding, knowledge work, research, visual understanding, and multi-step workflows. Anthropic says Opus 5.5 produces output more than 30% faster than Opus 5 and typically uses fewer tokens for the same work. Its default effort is also medium, while thinking is always enabled.
That means many old prompting habits are becoming unnecessary.
The biggest shift is this:
Stop micromanaging the model’s thinking. Start defining the outcome, boundaries, evidence, and finish line.
Here are the 12 rules developers should know.
