The new rules of context engineering for Claude 5 generation models

Summary

Then and nowThere were a number of previous context engineering best practices that had become myths. Including:.Then: Give Claude rulesNow: Let Claude use judgementWhen we first rolled out Claude Code, we needed to be sure that Claude avoided worst case scenarios, such as deleting files. This meant we would give particularly strong guidance that might not always be true, For example, in the system prompt we used to say: In code: default to writing no comments. Never write multi-paragraph docstrings or multi-line comment blocks — one short line max. Don't create planning, decision, or analysis documents unless the user asks for them — work from conversation context, not intermediate files.But for a certain subset of prompts, this guidance would be wrong. In the case of documentation, the user may have their own preferences, or specific parts of very complex code might need multi-line comment blocks.Still, without these guardrails for older models, the comments Claude wrote would be incorrect in many cases and we had to accept this tradeoff. But newer models have better judgement and can handle these decisions well without explicit rules. In the new system prompt we say: Write code that reads like the surrounding code: match its comment density, naming, and idiom.Then: Give Claude examplesNow: Design interfacesThe number one rule for tool usage was to give Claude examples on how to use them. With our newest models, we’ve found that giving examples actually constrains them to a certain exploration space. Instead of using examples, think more about the design of your tools, scripts and files- what parameters does Claude have and how can they be more expressive? For example, in the Todo tool example, just listing status as an enumeration between pending, in_progress, and completed, hints to Claude about how to use it. The instruction on keeping one item in_progress helps define our requested behavior.Then: Put it all upfrontNow: Use progressive disclosureBecause Claude ...