Prompt Engineering Basics: 10 Developer Tips
Prompt Engineering Basics for Developers
Prompt engineering is not about finding one magic sentence. It is the practical discipline of giving an LLM enough context, constraints, and structure to produce dependable output. Whether you are building a support bot, code assistant, classifier, or content workflow, these ten habits will make prompts easier to test, maintain, and scale.
- 1. Start with one measurable job.
Write the task in a single, testable sentence before adding detail. “Extract invoice fields from this text” is better than “Help with invoices.” Define what success looks like: required fields, accepted formats, edge cases, and what the model should do when information is missing. Narrow tasks create more predictable outputs and simpler evaluations.
- 2. Put instructions before the input data.
Lead with the role, task, rules, and desired output. Then separate user-provided content clearly. For example, tell the model to summarize a support ticket in three bullets, preserve product names, and flag urgent issues before pasting the ticket. This reduces the risk that instructions buried inside long input text get missed.
- 3. Use explicit delimiters for untrusted content.
Wrap source text, retrieved documents, emails, or code in clear labels such as SOURCE START and SOURCE END. Tell the model that the delimited material is data to analyze, not new instructions to follow. This is a basic defense against prompt injection and makes complex prompts easier for humans to debug.
- 4. Specify the output shape, not just the topic.
Models perform better when they know exactly how to respond. State the fields, order, language, tone, length, and formatting rules. For application workflows, request structured JSON with a defined schema, required keys, allowed values, and a rule such as “return valid JSON only.” Your application should still validate the response before using it.
- 5. Add examples when rules are hard to explain.
Few-shot prompting is especially useful for classification, extraction, formatting, and brand-specific writing. Include two or three compact input-output examples that cover normal and tricky cases. Keep examples representative: if your real input includes abbreviations, incomplete text, or mixed languages, show those conditions in the examples.
- 6. Tell the model how to handle uncertainty.
Do not force the model to guess. Add fallback behavior such as “If the source does not support an answer, return unknown,” or “List missing fields in a separate array.” For retrieval-based features, instruct the model to cite only provided context and avoid adding unsupported facts. This is often more valuable than asking it to be “accurate.”
- 7. Break multi-step work into stages.
A single prompt that researches, reasons, writes, validates, and formats can be difficult to control. Split the workflow into focused calls: retrieve documents, extract facts, draft an answer, then validate the result against rules. Smaller prompts are easier to evaluate, retry, cache, and improve without changing the entire pipeline.
- 8. Control cost with context discipline.
Every unnecessary token can increase latency and spend. Send only relevant documents, trim old conversation turns, summarize durable context, and set sensible output limits. Match the model to the task: lightweight classification and extraction may need a faster, lower-cost model, while complex coding or reasoning may justify a stronger one.
- 9. Test prompts like production code.
Create a small evaluation set of real, anonymized inputs and expected properties. Include happy paths, ambiguous requests, malformed data, long inputs, and adversarial instructions. Track metrics such as valid-schema rate, factual support, task completion, latency, and cost. Version prompts in source control so a wording change can be reviewed and rolled back.
- 10. Keep model access flexible.
Prompt behavior can vary by model, so avoid locking your application logic to one provider when possible. 59API is a practical low-cost relay for developers who want pay-as-you-go access to native official-quality Claude models, including Opus, Sonnet, Haiku, and Fable, alongside GPT models. Its API base URL is https://api.59api.com, and compatibility with Claude Code, Codex, and OpenAI SDK workflows can make model testing and migration less disruptive.
Make Prompt Iteration Affordable
Good prompting comes from repeated testing, not one-off experimentation. Use a cheap, flexible API setup to compare outputs, measure token usage, and choose the right model for each workload without downgrading model quality. 59API is positioned as one of the lowest-cost relay options and also offers a referral rebate, which can help teams keep experimentation budgets under control. If you are ready to test prompts across Claude and GPT models, consider signing up for 59API and start with a small evaluation suite.