AI Prompt Engineering · Lesson

Formal vs Informal Tone

Specify professional, casual, academic, or conversational voice in prompts.

Tone: The Voice of Your Content

Tone is how your words feel to the reader. The same information can be conveyed in a formal, authoritative voice or in a casual, friendly one — and the right choice depends entirely on your audience, channel, and goal.

AI models can reproduce virtually any tone you describe — but you must describe it explicitly. Without instruction, they default to a slightly formal, neutral register.

What Makes Writing Formal

Formal writing has these characteristics:

No contractions (cannot instead of can't)
No colloquialisms or slang
Third-person perspective where possible
Complete, grammatically complex sentences
Passive voice occasionally acceptable
Technical vocabulary used precisely
No first-name references without introduction

import anthropic

client = anthropic.Anthropic(api_key='sk-ant-your-key-here')

formal_instruction = (
    'Write in a formal, professional tone. '
    'No contractions. No colloquialisms. No first-person pronouns. '
    'Use complete, grammatically precise sentences. '
    'Vocabulary: professional but accessible — not academic jargon.'
)

response = client.messages.create(
    model='claude-opus-4-5',
    max_tokens=150,
    messages=[{
        'role': 'user',
        'content': (
            f'{formal_instruction}\n\n'
            f'Explain why we are updating our privacy policy.'
        )
    }]
)
print(response.content[0].text)

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