LLM Structured Output & JSON Schema Validator
Validate LLM JSON responses against JSON Schema and check OpenAI / Anthropic strict constrained-decoding rules (additionalProperties, required keys).
Eliminating Broken JSON Parsing in Agentic Pipelines
Production AI agents cannot rely on regex-scraping markdown code fences out of free-form LLM text. Constrained decoding (Structured Outputs) guarantees schema adherence—provided your JSON Schema satisfies strict provider invariants like additionalProperties: false and complete required arrays at every nested object level.
Use this validator to test both payload conformance and strict-mode schema readiness before deploying tool definitions to production.
How to Audit Your Structured Output Schema
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Frequently Asked Questions
Why do OpenAI and Claude strict structured outputs require additionalProperties: false?
Constrained decoding compiles your JSON Schema into a context-free grammar mask over token probabilities. Disallowing arbitrary extra keys bounds the grammar deterministically so the model cannot hallucinate undeclared fields.
