Structured Output Prompting: Get JSON, Not Prose

When you need data your code can use, don't ask for an explanation—ask for a schema. Show the model the exact keys, types, and an example object, then say "return only valid JSON, no markdown." A concrete template like {"sentiment":"positive|negative","score":0.0} removes ambiguity that a vague "list the results" invites.

Constrain values explicitly: use enums for categories, arrays for lists, and state whether fields are required. Add a fallback rule such as "use null if unknown" so the model never invents keys or drops them. For repeated jobs, keep the same prompt template and only swap the input—consistent structure in means consistent structure out.

On B4AI you can run the same structured prompt across several models and compare which one holds the format most reliably before wiring it into a pipeline. Always validate the output against your schema in code; treat a parse failure as a signal to tighten the instruction, not to loosen your parser.