AI JSON Schema Enforcer

Auto-fix JSON to match a schema — coerce types, drop extras, fill required fields.

  • 100% client-side · your data never leaves your browser
  • Instant, no rate limits
  • Free, no sign-up

AI-assisted — rule-based today.These tools use deterministic heuristics in your browser (no model API calls, no upload). We're validating demand before wiring real LLM backends.

JSON data
JSON Schema
Enforced JSON

Paste data and schema to enforce.

Enforcement log

Fixes applied by rule-based schema enforcement appear here.

Overview

AI JSON Schema Enforcer — Auto-Fix JSON to Match Schema

Force JSON data to conform to a JSON Schema — automatically coerce types, remove disallowed properties, add missing required fields, trim strings, and clamp numbers. Built for LLM structured-output pipelines where models drift from your contract. Rule-based enforcement today; same controls ready for AI-assisted repair later.

No uploadsNo sign-upOpen source
  1. Schema enforcement for AI pipelines

    Function-calling and structured output still produce extra fields, stringly-typed numbers, and missing keys. Validation alone rejects bad payloads; enforcement transforms them toward compliance so downstream code can proceed.

  2. Enforcement options

    • Remove extra properties when additionalProperties is false
    • Add missing required fields (null or schema default)
    • Coerce strings to numbers/booleans when the schema type demands it
    • Trim strings to maxLength and clamp numbers to min/max
  3. Gate LLM structured output

    Function calling and JSON mode get models close to your schema, but not always all the way — an id arrives as "42" instead of 42, an extra commentary field sneaks in, or a required key is missing. Dropping the response is wasteful when the data is basically right. Enforcement nudges the payload into shape so your pipeline keeps moving, with a validation pass as the final gate.

  4. Enforce then validate

    Enforcement and validation are complementary. Run the enforcer first to coerce types, fill required fields, and strip extras, then run the JSON Schema Validator to confirm the result actually conforms. Rules that can't be fixed automatically — cross-field constraints, complex conditionals — surface as validation errors for a human to resolve.

FAQ

Frequently asked questions

How do I make JSON match a schema?

Provide the JSON and a JSON Schema; the enforcer coerces types, removes disallowed properties, adds missing required fields, and clamps values toward compliance.

Does this replace JSON Schema validation?

No. Use enforcement to fix data, then validate to confirm. Some complex schema rules may still need manual edits.

Is this AI-powered?

Today it uses deterministic schema rules with no LLM API calls, so results are repeatable and private.

Is it useful for LLM output?

Yes. It's designed to reconcile function-calling and JSON-mode responses that drift from your schema before they reach production code.

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