Structured Output

JSON Output Prompt Builder

Stop parsing prose. Define the task and the schema, and get an output-contract prompt — field definitions, a realistic example response, validation rules, and strictness-controlled output rules. JSON first; YAML, XML, and CSV as modes.

What should the model do before returning the data? E.g. "Process the customer details in the input and return them as a structured record."

Output Format

JSON is the primary format — the others reuse the same contract engine.

Strictness Level

Strict adds the full no-prose, no-fences, exactly-one-object rule set.

Schema Fields *

The contract's heart: every field with its type, requirement, and meaning. Reorder with ↑ ↓.

Schema Preview (live example — not the output)

                
            

AI Resource Library

Resources for this tool

View All Resources →

Workflows

Workflows that use this tool

All Workflows →

Projects

Projects that use this tool

Browse the project catalogue →

How it works

Describe the task, pick the output format (JSON by default — YAML, XML, and CSV are modes of the same engine), set the strictness level, and build the schema: every field with a name, type, required flag, and description. The schema preview shows a live example of exactly what your prompt will enforce — name-aware sample values included, so an email field previews as user@example.com, not "string". Click Generate JSON Prompt and the builder assembles the full output contract: the task, the schema with field meanings, a realistic example response, validation rules, and strictness-controlled output rules. Nothing leaves your browser.

Best for

  • Forcing parseable, machine-readable output — JSON first, plus YAML, XML, or CSV
  • Building an output contract a downstream system can rely on
  • Stopping the model from wrapping data in prose or markdown fences

Not for

  • Pulling specific fields out of messy text — that is the Extraction Prompt Generator
  • Checking output you already have against a format — that is the AI Output Validator

Use cases

  • Getting parseable JSON from chat models that keep adding prose and markdown fences
  • Defining the response contract for OpenAI, Claude, or Gemini API calls
  • Feeding reliable structured data into Zapier, Make, or n8n automations
  • Standardizing one schema across a team so every prompt returns the same shape

Pro tips

  • Start with Standard strictness. Switch to Strict only when you see prose or fences leaking through — Strict's nine-rule block costs tokens on every call.
  • Field descriptions are not decoration: 'severity — critical, high, medium, or low' constrains the value space. The more a description sounds like validation, the better the output.
  • The example response in the prompt is doing heavy lifting — models follow examples more reliably than rules. That's why the builder generates realistic sample values instead of "string".
  • Using a model with native JSON mode? Keep the schema and validation sections anyway — native mode guarantees syntax, not your field names, types, or null discipline.

FAQ

How is this different from the Extraction Prompt Generator?

This tool defines the output's structure — the contract any task returns its data in. Extraction is a specific task: pulling fields out of unstructured text. They'll often be used together, but this tool doesn't care what the task is; it cares that the response parses. When the task IS extraction, start with the Extraction Prompt Generator and come back here to tighten the format.

Why is there no separate XML or YAML tool?

Because the format is a serializer, not a product. The contract engine — schema, example, validation rules, strictness — is identical for JSON, YAML, XML, and CSV; only the rendering changes. One tool with format modes beats four tools that are 85% the same.

What exactly does the strictness level change?

The OUTPUT RULES block. Flexible asks politely (two rules). Standard adds the no-fences, no-surrounding-text, null-for-unknown set. Strict adds the full battery: output only valid JSON, no explanations, no commentary, no markdown, no code fences, exactly one object, schema followed exactly, null over invention, no trailing commas.

Do I still need this if my model has a native JSON mode?

Native JSON modes guarantee syntactically valid JSON — they don't guarantee your schema. Field names, types, required-vs-null discipline, and value constraints still come from the prompt. The generated contract works alongside native modes; the strictness rules simply become cheap insurance.

How does it handle nested data — arrays and objects?

Array and object field types render correctly in JSON, YAML, and XML, including in the example response. CSV is flat by nature: the builder warns you, and the contract instructs the model to join multiple values with "; " inside cells. For genuinely nested data, the warning will point you back to JSON.

Why does the example use realistic values like user@example.com?

Models imitate examples more faithfully than they follow rules. An example with "email": "string" teaches the model that placeholder text is acceptable; an example with a realistic value teaches the shape AND the content style. The sample generator is name-aware for exactly this reason.