A language model is a probabilistic text generator with no notion of truth and no memory between calls. Building well means designing a system that produces reliable outcomes from an unreliable component, which is an engineering problem rather than a prompting one.
Fluency is not accuracy
The model produces text that reads as confident regardless of whether it is correct. Fabricated citations, invented function names and plausible wrong numbers all arrive in the same authoritative tone, so the system must verify rather than trust.
No state between calls
Each request is independent. Anything the model should know — conversation history, retrieved documents, user context — must be sent every time. This shapes cost, latency and the entire architecture.
Non-determinism is the design constraint
The same input can produce different output. Every downstream component must handle variation, which means parsing defensively, validating structure and deciding what happens when the output is unusable.
Action step
Send the same prompt ten times and record how much the outputs vary. That variance is what your system must tolerate.
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