Practical Prompt Engineering Lessons from Using Claude Code

What Worked: Shipping Production Code

The user, a project manager without a development background, successfully built and shipped production code using Claude Code. The resulting application runs in a browser and includes over 1,200 tests.

The Core Challenge: Prompt Quality

The primary difficulty identified was that Claude Code will produce poor or incorrect results if prompts are not precise. The user states it "will absolutely let you walk into a wall at full speed if your prompt isn't airtight."

Three Techniques That Improved Results

• Two-Phase Prompts: Instead of writing prompts in one pass, the user adopted a two-phase approach. Phase 1 involves writing the what in your own domain language, including rules and desired outcomes. Phase 2 involves rewriting the prompt from the perspective of a reliability engineer, adding verification gates, single objectives, explicit session boundaries, and anti-shortcut rules. The user found that one phase yields decent results, but two phases yield production-grade results.
• One Prompt = One Objective: Bundling multiple goals into a single prompt consistently led to poor outcomes. Claude Code would prioritize one goal, merge them sloppily, or provide incomplete solutions for both. The user emphasizes "ruthless scope discipline" with one objective per prompt, calling this the biggest "quality multiplier" discovered.
• Specific Role Definitions: Generic role instructions like "Act as a senior developer" were found to be "nearly useless." Effective roles must name the exact combination of expertise required for the task. The user provides an example: "Conservatory-trained music theorist who has built commercial composition engines" produces fundamentally different and better results than a vague instruction like "music expert." Specificity changes the model's underlying thinking process, not just the tone of the output.