SchemaCraft Studio

Frontier Schema Engine

JSON, JSON5, Python dicts, & NDJSON → strict Pydantic v2, Zod, TypeScript, & Frontier AI schemas.

Zero Cloud Egress
Frontier AI Formats
No Account Required

Root:

Input Stream

Standard JSON

{
  "booking_id": "bk_9f4c3a12-8e1b-4f72-9852-c62d08a5f331",
  "pnr": "NOR742",
  "status": "CONFIRMED",
  "created_at": "2026-08-21T15:30:00Z",
  "passengers": [
    {
      "passenger_id": "pax_01",
      "first_name": "Sarah",
      "last_name": "Connor",
      "email": "sarah.connor@skyline.org",
      "loyalty_tier": "PLATINUM",
      "checked_bags": 2,
      "special_meal": "VEGAN"
    },
    {
      "passenger_id": "pax_02",
      "first_name": "John",
      "last_name": "Connor",
      "email": "john.connor@skyline.org",
      "loyalty_tier": "GOLD",
      "checked_bags": 1,
      "special_meal": null
    }
  ],
  "itinerary": {
    "flight_number": "NA-204",
    "origin": "SFO",
    "destination": "HND",
    "departure_time": "2026-09-15T11:45:00Z",
    "arrival_time": "2026-09-16T15:30:00Z",
    "duration_minutes": 645,
    "cabin_class": "BUSINESS"
  },
  "payment": {
    "amount": 3420.5,
    "currency": "USD",
    "is_settled": true,
    "receipt_url": "https://pay.norai.dev/receipts/rec_891274"
  }
}

Generated schemas will appear here in real time.

Valid AST•0 fields•0 models•depth 0•0ms

100% In-Browser/0 Byte Egress

Deterministic client-side inference pipeline

Transform unformatted JSON, Python dictionaries, or NDJSON logs into validated schemas in sub-millisecond execution time — 100% in your browser.

PHASE 1INGESTION

Universal Ingestion & Tolerant Parsing

Accepts standard JSON, relaxed JSON5, Python dict literals with True/False/None, or multi-line NDJSON streams. Unquoted keys or trailing commas are parsed cleanly without throwing exceptions.

JSON · JSON5 · Python Dict · NDJSON

PHASE 2OFF-THREAD

Web Worker AST Inference

Parsing, type inference, enum collapsing, and structural merging run inside a dedicated background Web Worker. Your main thread stays responsive at 60–120 FPS even when processing massive multi-megabyte payloads.

0 Main Thread Lag · Sub-10ms

PHASE 3EMISSION

Compiler-Strict Schema Emission

Emits production-ready code with exact provider constraints — OpenAI strict mode, Pydantic v2 ConfigDict, and Zod v3 validators. Complete with SDK snippets and multi-dialect ZIP bundle exports.

8 Dialects · SDK Snippets · Zip Bundle

Supported dialects & compiler contracts

Every dialect emitted by SchemaCraft conforms to the exact compiler constraints, runtime rules, and grammar restrictions of its host ecosystem.

openai_tool.json•GPT-4o · o1 · o3-mini

Rule:OpenAI's grammar sampler constrains output tokens during decoding. Every property must be listed in 'required', and every object must set 'additionalProperties: false' to eliminate out-of-schema hallucinations.

{
  "type": "function",
  "function": {
    "name": "FlightBooking",
    "strict": true,
    "parameters": {
      "type": "object",
      "properties": {
        "booking_id": { "type": "string" },
        "passenger": {
          "type": "object",
          "properties": {
            "name": { "type": "string" },
            "loyalty_tier": {
              "type": "string",
              "enum": ["GOLD", "PLATINUM"]
            }
          },
          "required": ["name", "loyalty_tier"],
          "additionalProperties": false
        }
      },
      "required": ["booking_id", "passenger"],
      "additionalProperties": false
    }
  }
}

Why SchemaCraft wins

Legacy converters were built for the pre-LLM era. SchemaCraft ships frontier structured-output formats and hardened validators while staying a zero-egress, offline-first studio.

Capability	SchemaCraft	QuickType	Legacy converters
Frontier AI output formats	OpenAI Strict, Anthropic, Gemini, MCP	None — generic types only	Rare / partial
Python validation	Pydantic v2 · extra="forbid"	Stuck on Pydantic v1	Unmaintained
Privacy & ads	100% in-browser · zero ads	Cloud upload · ad banners	Cloud + tracking
Input tolerance	JSON · JSON5 · Python dicts · NDJSON	Strict JSON	Strict JSON
TypeScript & Zod v3	Interfaces + z.infer	Legacy type aliases	Outdated
Account required	Not required	Not required	Not required

Frequently answered questions

Technical specifications on schema grammar, offline Web Worker execution, Pydantic v2 migrations, and zero-egress privacy.

01Is my data private when using SchemaCraft?

Completely. All parsing, type inference, and code generation execute exclusively inside an in-browser Web Worker. No payload content ever leaves your machine — there is zero cloud egress, zero logging, and no network requests. SchemaCraft works fully offline after initial page load.

02Why does OpenAI Structured Outputs require additionalProperties: false?

OpenAI Structured Outputs decode tokens against your grammar, ensuring the model cannot invent unseen keys. A root object with every property marked as required and additionalProperties: false enables the sampler to guarantee the output conforms to your schema. SchemaCraft enforces this automatically in OpenAI Strict mode and Pydantic extra='forbid' mode.

03Why generate Pydantic v2 instead of Pydantic v1?

Pydantic v2 is powered by a Rust core that validates payloads 5–50× faster, supports native ConfigDict, and handles discriminated unions out of the box. SchemaCraft emits modern model_config = ConfigDict(extra='forbid') patterns that map directly onto FastAPI, instructor, and OpenAI tool-calling pipelines.

04How does SchemaCraft handle dirty or malformed JSON?

Its universal parser tolerates JSON5, relaxed Python dict literals (with True, False, None, and trailing commas), and multi-record NDJSON streams. It infers a unified schema across all samples and surfaces line/column error callouts if syntax is unrecoverable.

05How does SchemaCraft handle array items with evolving or heterogeneous types?

When an array contains objects with varying fields, SchemaCraft performs structural type unioning. Shared fields remain required, divergent fields become optional, and primitive type mixtures resolve into clean TypeScript unions (e.g., string | number) or Python unions (e.g., str | int).

06Can I use generated schemas directly in FastAPI or Next.js API routes?

Yes. Pydantic v2 code is 100% standard Python ready for FastAPI request and response models. Zod schemas export both runtime validator objects and inferred TypeScript types (z.infer<typeof Model>) ready for tRPC, Next.js Server Actions, and Route Handlers.

07Does SchemaCraft work completely offline?

Yes. Once the page shell and Web Worker are cached by your browser, generation requires zero active internet connection. There is no remote API dependency, so SchemaCraft functions seamlessly on air-gapped machines and in high-security corporate networks.

08What is Model Context Protocol (MCP) and how does SchemaCraft support it?

Model Context Protocol (MCP) is the open standard developed by Anthropic for connecting AI models to external tools and data sources. SchemaCraft generates production-ready JSON-RPC 2.0 tool definitions with valid inputSchema manifests ready for Claude Desktop and Cursor agents.

09How is SchemaCraft different from QuickType and legacy converters?

QuickType and older web utilities were built before LLM structured outputs. They lack OpenAI strict mode, emit outdated Pydantic v1 syntax, often upload payloads to cloud servers, and clutter their interfaces with ad banners. SchemaCraft is purpose-built for AI engineers: zero egress, Pydantic v2, Zod v3, MCP manifests, and sub-millisecond tactile feedback.

10How do I export all dialects at once?

Click Export in the workstation inspector to download a complete .zip bundle containing Pydantic v2, Zod, TypeScript, OpenAI Strict, Anthropic, Gemini, MCP, and JSON Schema files plus synthetic mock JSON — generated entirely in your browser.

Ready to generate schemas?

Zero cloud egress. 100% in-browser Web Worker. No signup, telemetry, or remote API dependencies.

Open Workstation