Prompt for reliability, not just capability
Clear instructions, explicit constraints, worked examples, and a defined notion of done make an agent behave consistently instead of creatively.
Be explicit about the boundaries
Most inconsistency comes from ambiguity. Spell out what the agent may and may not do, what a finished task looks like, and what to do when it is unsure. An agent told to ask a clarifying question or refuse when information is missing is far more reliable than one left to guess.
Show, do not just tell
A couple of concrete examples of good behavior anchor the model more effectively than a paragraph of description. Examples are especially powerful for edge cases, where a single demonstration of the right handling prevents a class of mistakes.
Keep instructions stable and versioned
Prompts are code. A reworded instruction can shift behavior in ways you will not notice without measurement, so version prompts and re-check reliability when they change.
Key takeaways
- Remove ambiguity: define what done means and what to do when unsure.
- Give worked examples, especially for the tricky edge cases.
- Treat prompts as versioned code and re-measure after every change.
Further reading
- Building effective agents AnthropicAnthropic's guide to how effective agents are structured and where they commonly break down.