Four Claude Code Hooks Enforce Voice and Tone Consistency in AI-Written Copy

A developer has implemented a system using four Claude Code hooks to enforce voice and tone consistency when AI agents write copy. The approach addresses the problem where AI-generated content gradually drifts off-brand through hedging phrases and generic language.

Hook Implementation

The system uses four specific hooks:

• UserPromptSubmit hook: Detects VOICE-AND-TONE.md files and injects an instruction to delegate to a reviewer agent before editing any copy file
• PreToolUse hook: Blocks Edit/Write calls to copy-bearing files (.tsx, .md) unless a session marker exists
• PostToolUse hook: Creates the session marker after the reviewer completes its work
• Stop hook: Removes the marker after each response, so the next turn starts locked and requires a fresh review

Reviewer Agent Design

The reviewer is a Claude Code agent with read-only tools (Read, Glob, Grep). It reads the voice guide, reads the proposed copy, and reports violations with:

• The offending text
• The rule it breaks
• A suggested fix

The reviewer cannot edit files directly, maintaining separation of concerns.

Key Design Philosophy

The system functions as a gate rather than a nudge. A missed voice review means off-brand copy could ship to production. The developer notes that the cost of one agent call before editing is lower than the cost of finding and fixing drift after the fact.

The full implementation includes hook code, agent definition, and a starter template for voice guides. The developer asks whether others have built similar hooks for non-functional constraints like accessibility or coding standards.