Use system prompts wisely

Every request pays the system prompt tax

System prompts run on every single request. A bloated system prompt is the most expensive per-token waste in any Claude app because it multiplies across every call.

What belongs in a system prompt

• Role and persona definition (brief)
• Output format requirements
• Hard constraints ("never mention competitors")
• Any context that applies to every turn

What doesn't

Examples, lengthy explanations, one-time context, or anything that only applies to a specific turn. Move those to the user message where they're needed.