When customizing Claude for your use case, you have two main approaches:

Prompting (Recommended First)

• No training required
• Instant iteration
• Works for most use cases
• Use system prompts, few-shot examples, and RAG

Fine-Tuning

• Better for style/format consistency at scale
• Requires labeled training data
• More expensive and slower to iterate
• Best when prompting hits a ceiling

Anthropic's guidance: exhaust prompting before considering fine-tuning.

Reference:

Fine-tuning documentation

https://docs.anthropic.com/en/docs/build-with-claude/fine-tuning