Which JSON Schema version does it output?

It emits JSON Schema draft-07, the version most widely supported by validators and by structured-output features in major LLM APIs. The output is plain JSON you can paste anywhere.

How are arrays handled?

For an array, the tool infers a schema from the first element and uses it as the items schema. If your arrays hold mixed shapes, review and merge the item schema by hand.

Does it mark fields as required?

By default it lists every property of an object in a required array, since the sample contained them. Remove entries that are actually optional before using the schema for validation.

Is my data sent anywhere?

No. Inference happens entirely in your browser with no network calls, so you can safely paste responses that contain sensitive content.

Why use an inferred schema?

A schema lets you enforce structured output from an LLM, validate responses before parsing, or document the shape your code expects. Inferring from a real sample is faster than writing one from scratch.

API Response Schema Inferrer

API response schema inferrer

When you call an LLM API and get back structured JSON, you often want a schema: to enforce that shape with structured outputs, to validate responses before parsing, or just to document what your code expects. Writing one by hand is tedious. This tool reads a real sample and produces a JSON Schema draft-07 describing it, instantly and entirely in your browser.

How it works

The tool parses your JSON and recursively walks the value tree. Strings, numbers, booleans, and null map to their JSON Schema types; objects become type: object with a properties map and a required list of their keys; and arrays become type: array with an items schema inferred from the first element. The result is a self-contained schema document you can copy and drop into a validator or an LLM structured-output config.

Tips and notes

Inferred required is a starting point. Every key in the sample lands in required. Delete the ones that are genuinely optional before validating real traffic.
Mixed arrays need a manual merge. Item schemas come from the first array element only. If your arrays vary, combine the variants by hand.
Add constraints after inference. The tool gives you types and structure; add enums, formats, minimums, and patterns yourself to make the schema strict.
Great for function calling. The inferred object schema drops cleanly into a tool or function parameter definition for OpenAI or Anthropic.