Fine-tuning takes an already trained model and continues training it on a focused dataset, adjusting its weights so it performs a specific task or follows a particular tone better than the general model does.
Why it matters
It can improve consistency on narrow jobs such as classifying support tickets or writing in a brand voice, and sometimes lets a smaller, cheaper model match a larger one. It is mainly useful for behavior and format, not as a reliable way to add fresh facts; RAG suits that better.
Example
Training examples are often prompt and ideal-response pairs:
{"prompt": "Ticket: I forgot my password",
"completion": "category: account_access"}
A few hundred to a few thousand clean examples may be enough for a narrow task, depending on the model and goal.
Common mistakes
- Fine-tuning before trying better prompts or retrieval.
- Using noisy or inconsistent examples, which teaches the model the noise.
- Skipping a held-out test set and missing overfitting.
Related
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