Stop Wasting Tokens: 5 Engineering Prompts to Save Cost and Time

We've all been there. You ask the AI a simple question, and it spits out three paragraphs of polite conversation, a disclaimer about its knowledge cutoff, and finally—maybe—the code you wanted.

This isn't just annoying; it's expensive. Every token counts, especially when you're working with large codebases.

Here are 5 professional prompt engineering techniques to cut the fluff and get straight to the logic.

1. XML Fencing (The Anthropic Standard)

Claude models are trained significantly on data structured with XML tags. It helps the model understand boundaries.

Bad Prompt: "Here is my code: [code] and here is my error: [error]. Fix it."

Pro Prompt: Use XML tags like <component_code> and <error_log> to clearly separate different parts of your input.

2. The "Prefill" Magic

This is a little-known trick for the API. You can actually start the assistant's response for it.

If you want JSON, don't just say "Return JSON". By forcing the model to start with a curly brace, you bypass all the "Sure! Here is the JSON data..." introductory fluff. It saves tokens and forces strict formatting.

3. Chain of Thought (CoT)

For complex debugging, don't ask for the answer immediately. Ask for the thought process.

Add this instruction: "Think step by step inside tags before outputting the code."

This improves accuracy by 30-40% on logic puzzles and complex refactors because it allows the model to "draft" its response.

4. "Output Only"

Be explicit about what you don't want.

Template: "Return ONLY the code block. Do not provide explanations. Do not provide conversational filler."

5. The Role & Constraints

Always define who the AI is.

"You are a Senior React Engineer. You prefer functional programming patterns. You dislike useEffect unless absolutely necessary."

Summary

Prompt engineering is just programming in natural language. The more specific, structured, and constrained your input is, the higher quality your output will be.

Start treating your prompts like code, and watch your productivity (and token savings) multiply.