Using Claude to analyze writing patterns for better custom instructions

A Reddit user shared a method for creating more effective custom instructions for Claude by having the AI analyze actual writing samples rather than relying on subjective descriptions of tone.

The problem with standard custom instructions

The user notes that typical advice for custom instructions involves pasting examples and adding lines about tone, but this only works for a few messages before Claude drifts back to default behavior. The issue is that custom instructions describe voice from memory - you write down what you think you do ("direct," "uses short sentences," "avoids jargon"), which captures only a fraction of what makes your writing distinctive.

The analysis method

The user collected 10 writing samples across different formats and fed them to Claude with a specific request: identify concrete patterns rather than summarizing tone. Patterns that emerged included:

• Which punctuation you avoid entirely
• Where your analogies come from
• Specific word choices (e.g., "I never use the word 'ensure'")

These were patterns the user had been doing for years without consciously noticing them.

Implementation and results

After Claude identified these concrete patterns, the user organized everything into a structured document and used it as a system prompt. The difference was immediate - Claude stopped drifting because the guide was specific enough to anchor it. The user emphasizes that "I never use the word 'ensure'" is a useful instruction, while "I write in a direct tone" is not.

The Reddit post mentions that a training guide has been published for those who want to know how to implement this method themselves.