imtiazrayhan The reliable way to get data (not prose) from an LLM is to give it a schema and validate against it. This skill builds that schema from a concrete example of what you want back, then wires it into a structured-output call — so the model returns typed, validated objects and your code stops parsing free-form JSON by hand.
This is distinct from generating test fixtures (that's a mock-data factory) and from documenting an existing API (that's an OpenAPI doc writer): here the output is the schema the LLM must conform to.
When to use this skill
- Adding typed/structured output to an LLM feature (extraction, classification, form-filling).
- Replacing fragile
JSON.parse+ try/catch around model output with a validated schema. - Designing the exact shape for an extraction or tool-output contract.
Instructions
- Start from a real example. Take a representative sample of the desired output (or a few). Infer fields and types from the data, not from a guess — and gather a couple of edge-case examples so optionality and unions are right.
- Type precisely. Choose specific types (int vs. float, date vs. string), mark genuinely optional fields optional and required fields required, and use enums for closed sets rather than free strings.
- Add model-facing descriptions. Field descriptions are prompt surface in structured-output libraries — say what each field means, with units and formats ("ISO 8601", "USD cents"). This improves the model's accuracy, not just documentation.
- Constrain to make bad output impossible. Add bounds, patterns, and enums so invalid values can't validate. Prefer a flatter shape where it doesn't lose meaning — deeply nested schemas are harder for models to fill correctly.
- Emit in the target stack. Generate the schema as Pydantic (Python), Zod (TypeScript), a
.bamltype, or JSON Schema — matching the structured-output tool in use (Instructor, BAML, or the Vercel AI SDK). - Wire and validate. Hook it into the structured-output call with retry-on-validation-failure, and test it against the original examples plus the edge cases.
[!TIP] Let the schema carry the instructions. A well-named field with a clear description and an enum often replaces a paragraph of prompt — see Structured Output vs JSON Mode vs Function Calling.
Output
A validated output schema in the target language, with typed/constrained fields and descriptions, wired into a structured-output call with retry — verified against the example outputs.